With the release of Windows 7, there are people who, for one reason or another, will still want to go back to Vista or XP. If you want to uninstall Windows 7 and revert to your previous OS, you may not be able to do so.
In this post I will walk you through all the options and scenarios for uninstalling Windows 7 from a computer that already had an operating system installed, such as Windows XP or Vista. If you need more information on Windows 7, check out my previous post on the differences between different versions of Windows 7
The first thing to note is that you can upgrade your Windows Vista computer to Windows 7, but not Windows XP. If you already have XP, you will have to do a clean install of Windows 7
However, if you have a Windows XP computer and you are installing Windows 7 UPPER than Windows XP, then you can actually go back to XP. So if you have an XP computer and want to upgrade to Windows 7, DO NOT format your hard drive! Just insert the disc, boot from the CD and install Windows 7.
In this case, Windows created a folder named Windows.old at the root of the Windows partition with the previous operating system and data. You can follow the step-by-step instructions on how to revert to a previous Windows installation after installing Windows 7.
Suppose you have upgraded from Windows Vista to Windows 7. In this case, you CANNOT go back to Windows Vista. This is a one-way process and you should keep this in mind when migrating from Vista to Windows 7.
To revert to Vista, you will need to do a clean install of Windows Vista, which means you will have to back up all of your data and then manually restore it later. You will also have to reinstall all your programs.
Finally, if you installed Windows 7 in a separate partition to create a multiboot system and now want to uninstall Windows 7, you can most likely uninstall it without messing up anything.
Note that this will only work if an older version of Windows was installed first. If you installed Windows 7 and then installed Windows XP or Vista to create a multiboot system, you cannot uninstall Windows 7.
If you installed Windows 7 as a second OS, you first need to download the old version of Windows to your computer and either delete or format the partition with Windows 7 installed on it.
You must do this so that the old version of Windows can free up disk space and use it. You can do this by right-clicking My Computer, selecting Manage and then clicking Disk Management in the left-hand list.
Right-click on the volume that Windows 7 is installed on and select Format or Delete Volume.
Now you need to remove Windows 7 from the multiboot screen. You can do this by going to Start, Control Panel, System and Security, Administrative Tools, System Configuration.
Click the Boot tab and click the list for Windows 7. Click Uninstall and then Restart.
This is it! After formatting the Windows 7 partition and removing it from the multiboot screen, you should be able to restart your computer and automatically load your previous Windows installation! Enjoy!