Virtually every new PC being sold today includes Windows Vista. However, Vista has not exactly been well received by the IT community. So what happens if you have a machine with Vista on it, but you really want to run Windows XP instead?
Locate the necessary drivers
Once you have procured a copy of Windows XP, the next step is to track down Windows XP-compatible device drivers for the computer(s) that you're downgrading. Some manufacturers only offer Vista-compatible drivers, but fortunately this seems to be the exception rather than the rule.
The one area where you might run into problems is when it comes to x64 drivers for Windows XP. Even when Windows XP was in its heyday, 64-bit drivers could be a bit hard to come by. Today, the situation is a little better because every new computer being produced has a 64-bit processor.
Create a backup
If you have data that you need to preserve or you're planning on blanking your hard drive, I recommend creating a full system state backup before you begin the downgrade process. That way, you will have something to fall back on should the process go belly up.
Although creating a system state backup seems self-explanatory, there is one thing that you need to think about. The version of NTBACKUP that comes with Windows Vista is not compatible with Windows XP. This is a big deal if you're planning on blanking your hard drive, because if you need to restore the backup you can always install Vista and then perform the restoration.
If you do have data that you need to preserve, use a third-party backup program so you can restore your data to Windows XP if something should go wrong later on. If you do not have a third-party backup program, then one option is to perform a file level copy of your data. You won't be able to perform a full-blown operating system restoration from the file level copy, but you can at least get your data back.
The downgrade process
Once you have all your ducks in a row, it's time to perform the downgrade. If you're planning to format your hard drive and then install a fresh copy of Windows XP, there's nothing special you need to know. If you're trying to perform the process without formatting your hard drive, you've got your work cut out for you.
Windows Setup will not allow you to perform a downgrade if a newer version of Windows is already installed on the system. Therefore, the trick to performing a downgrade is to make Setup think that no operating system is installed. I explain how to accomplish that below. Once that's done, you can install a clean copy of Windows XP and then manually remove Windows Vista. Keep in mind that the method I'm about to show you performs a clean install, so you will have to reinstall any applications that might be present on your system and manually copy all of your data to the desired locations.
With that in mind, insert the Windows XP installation CD and boot to the Recovery Console. Once you arrive at the command prompt, enter the following commands:
Ren Windows Vista
The first two commands overwrite the hard drive's boot sector, which tricks Setup into thinking that Windows XP was previously installed. The third command drops you down to the root directory and the fourth renames the Windows folder to Vista.
Once you have performed these commands, you should be able to boot Windows XP Setup and install Windows XP. When the setup process has completed, you can delete the Vista folder from your hard drive.
About the author: Brien M. Posey, MCSE, has received Microsoft's Most Valuable Professional Award five times for his work with Windows Server, IIS and Exchange Server. He has served as CIO for a nationwide chain of hospitals and healthcare facilities, and was once a network administrator for Fort Knox.