How to Reinstall Windows

The question how to reinstall Windows is often asked on the internet, so we wrote this post which is all about Windows reinstallation.

Under These Situations You May Need to Reinstall Windows

After running a Windows OS for a long time, you may encounter the following situation:
It takes more than 1 minute to start the computer and several minutes to make everything prepared. In addition, programs such as Microsoft Office, Photoshop, and Browsers should respond for a long time. Then, you made a virus scanning, but nothing is found.
Well, do you know what slows down the computer? Most of the time, the gradually increased file trashes, defragments, and so on are culprits. Under this situation, merely cleaning and defragging hard disk plays a minor role, and users had better reinstall Windows. After all, many tests show this is a good solution, and it also solved my problem.
Of course, making a system reinstallation might help you get out of trouble under many other conditions, for instance:

  • Anti-virus programs failed to clear some strong viruses.
  • System crashes due to system file corruption or boot file (bootmgr) damage.
  • Get black screen or blue screen error without knowing exact reason.
  • Separate Windows system partition from boot partition.

Something about Windows System Partition and Boot Partition
On Windows platform, there are 2 partitions used to start Windows, namely system partition and boot partition. The partition saving Windows boot files like boot manager is called system partition while the partition storing system files is actually called boot partition. Before Windows 7, system partition and boot partition are the same partition (always Drive C), but along with Windows 7 they are separable, and the former is always hidden and 100MB for 32 bit system and 350MB for 64 bit system in size. Separating system partition and boot partition is good for preventing Windows boot files from being damaged since a hidden partition will not appear in Windows Explorer. Nevertheless, the system partition (shown as system reserved partition by Windows) will be generated only when users install Windows from scratch on an unpartitioned hard disk.
Now that reinstalling Windows can help us solve many problems, how can we make a wonderful reinstallation? Just reinstall Windows from USB flash drive or CD/DVD disc directly? It is of course not, and users need to do lots of preparations as well as pay much attention to some instructions. In this post, we will show users what they should do before, during, and after reinstalling Windows.

Make the Following 4 Preparations before Reinstalling Windows

1.Prepare Windows Installation Disc

We can install Windows from either Windows installation CD/DVD or USB flash drive. If you have such a disk, skip to the second step. If there is no such disk, create one by burning your Windows ISO file to optical disc or USB flash drive, and both Windows built-in burner and third party program can help do this.

2.Backup All Needed Data Saved on Boot Partition or System Disk
Generally, users would like to reinstall Windows to its original place. To be specific, if the old Windows OS is saved on partition C now, they are always hoping to reinstall system to the place where partition C is located. However, doing reinstallation will result in data loss no matter you delete the original partition or not. Therefore, when the partition is storing useful files, please backup or transfer these files out in advance, and Windows built-in Copy and Paste features are available. If there are dozens of GB files to backup, users had better clone the entire partition rather than copy files, because it will help save much time.
Tip: if you forget to make such a backup and Windows has been reinstalled to the original boot partition, there still might be a chance to recover needed files. Please see how to recover data after reinstalling Windows to get details.
Nevertheless, many users are more likely to make a clean reinstallation, namely installing Windows on an unpartitioned hard disk, since they hope to separate Microsoft system partition from boot partition. For this demand, they need to backup all needed files, and then clean the whole hard disk.
The fastest way to create a backup for all important files is copying the disk, and detailed steps are as follows:

  • Download MiniTool Partition Wizard (a freeware for Windows non-server users) and install it on computer.
  • Start and launch the program to get its main interface:


  • Select the system disk and choose “Copy Disk” feature from the left side. Then, select the disk that will be used to hold the backup and click “Next>”.


  • Edit partition size and location, and then click “Next>” to get a boot note. Then, click “Finish” to go back to the main interface.
  • Click “Apply” and “Restart Now” successively to make all changes performed in boot mode.
    For more details, please see Copy Disk.
    After the backup has been created, users may need to do the third preparation – create a clean place for Windows.
    3.Delete Windows Boot Partition or Clean System Disk
    If you just plan to reinstall Windows without deleting the boot partition, ignore this step, but we highly suggest deleting the boot partition and then reinstalling Windows since the latter gives better experience. Well then, how can we delete Windows boot partition?
    Unfortunately, Windows snap-in Disk Management tool does not allow users to delete the partition since it saves Windows which is running, and users have to look for other utilities. Here, we also suggest using MiniTool Partition Wizard. For more details, please see Cannot Delete Volumes in Windows.
    Well, if users want to separate system partition from boot partition, how can they clean the system disk? Some users think of using Clean command in Diskpart, but disappointingly it may not function when operating system on this disk is running. Therefore, a third party partition program is needed, and users can also employ the freeware MiniTool Partition Wizard whose Delete All Partitions function will give you great help.
    After boot partition is deleted or system disk is cleaned, users need to do the last preparation.
    4. Remove All Non-essential Peripherals
    Before starting the reinstallation, users had better remove all peripherals that are not required to reinstall Windows, such as card reader, earphone, and removable hard disk. With these devices connected, you may receive error message.
    Now all preparations have been done, so users can start reinstalling Windows OS. Please follow steps below.

    Detailed Steps to Reinstall Windows

    Taking the following operations, you can reinstall Windows OS with ease.
    Step 1: Set Boot Order in BIOS
    Start computer and press a required key to enter BIOS. If you do not know which key is correct, please search “how to enter BIOS plus your mother board’s type or computer trademark”.

    Then, navigate to the Boot menu by using “←” or “→” key on the keyboard. Under this menu, you can change boot order. If you are going to reinstall Windows from installation CD or DVD, place the CD-ROM Drive at the first place. However, if you just have a USB installation drive, give boot priority to Removable Devices. Well, how can we change the boot order? These 3 keys are needed, including “↑”, “↓”, and “−”. For example, if we want to move CD-ROM Drive to the first place (give boot priority to Windows installation CD or DVD), we need to take these operations: highlight Removable Devices via “↑” or “↓”, and then press on “−”. After that, the CD-ROM Drive option will be after Hard Drive. Next, highlight Hard Drive and press on “−”. Then CD-ROM Drive will be located at the top. At last, press on “F10” to save changes and quit from BIOS. Then, we can start reinstalling.
    Step 2: Reinstall Windows via Installation Disk
    Here, we take reinstalling Windows from DVD for example.
    After the boot order is set correctly, our computer will boot from Windows installation DVD as long as the optical disc has been inserted and detected.

    Then, specify preferred language, currency format, and nationality of your keyboard or input method and click “Next”. Next, choose “Custom (Advanced)” to get the window below:

    Now we can mark a place to hold Windows, which can be an existing partition or unallocated space. Select the space and click “Next” to continue. Once the installation is completed, users will be asked to type the product key so as to activate Windows. Just do as it requires and then make necessary system settings.
    After Windows is installed successfully, users need to optimize system by doing some necessary operations.

    Optimize Computer after Reinstalling Windows OS

    If you want to make your Windows OS run better, it’s very necessary to do the following operations:
    1.Align Partition(s) If the Reinstallation Is Made on SSD or 4k-sector HDD
    Tip: if you are using the traditional 512-sector mechanical hard disk, you can skip this step directly.
    4K alignment is a quite important issue for solid state drive (SSD) and 4k advanced format hard disk. Running programs on misaligned partition will slow down these program largely, and running Windows OS on misaligned partition will increase system boot time, access time, shutdown time, and so on. Therefore, it is quite necessary for SSD or 4k-sector hard disk users to check whether their partitions are aligned after reinstallation is done. Next, let’s see detailed steps to align partition(s) in Windows.
    Step 1: start and launch MiniTool Partition Wizard to get its main interface:

    Step 2: select target device to align. There are 2 choices: align single partition and align all partitions. If you want to align boot partition only, select the partition and choose “Align Partition” feature from the left side. However, if you hope to align all partitions on the SSD, please select the disk and choose “Align All Partitions” which will detect the entire disk and then tell you how many partitions to align in total.
    Step 3: click “Apply” to perform all changes.
    2.Extend Windows Boot Partition If It Does Not Have Much Free Space
    As we know, temporary files, caches, Windows updates, and some programs will be saved to boot partition automatically, which may make the very partition run out of space in one day. Therefore, it is very necessary to enlarge the boot partition if it does not have much free space left. Moreover, allocating more space to boot partition will make Windows run more smoothly. Well, how can we extend such a partition?
    Firstly, open Windows Disk Management tool to get its main window. Then, right click the boot partition to see whether “Extend Volume” feature is available. If it can be chosen, enlarge the partition by following instructions. If the option is grayed out, turn to the free partitioning tool MiniTool Partition Wizard since it can enlarge a partition by taking free space from any other existing partition or unallocated space on the same hard disk, and you can find detailed steps from our previous post Can’t Extend Boot Partition.
    3.Install Important and Recommended System Updates
    Installing updates can fix errors as well as bugs, but it should be done on the condition that there is network connection. Once the connection is available, please click Start button and type Windows Update in Search box. Then, click Check for updates. At last, follow instructions to install all essential and recommended system updates.
    4.Install Necessary Hardware and Software Drivers
    Reinstalling Windows may make previous hardware and software drivers missing. If you want to make the computer run normally, please install necessary drivers one by one, which can be got from your manufacturer’s website or third-party websites.
    5.Do Other Necessary Operations
    After all necessary updates and driver are installed, users need to restore their backup to Windows boot partition or drive C. Then, check whether the restored data can be used as usual. If not, redownload or reinstall. Next, download and install other necessary apps. Furthermore, if you fear of system crash, please create restore point or make a backup for your system. At finally, set power-on password.



    Now all operations which had better be done before, during and after Windows reinstallation have been shown. Following steps and instructions we introduce, you might get a wonderful Windows OS.


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