|If my research is correct, the Dell Dimension XPS model R400 is from 10-15 years ago. Back then, manufacturers provided the Windows OS disc along with drivers discs and other program discs. It wasn't until about 2005 that manufacturers really got into setting up a recovery partition on the hard drive to automate the process.|
If you lost those discs, you can possibly still find drivers for that old machine online somewhere. As for the Windows disc, use any one with the same version of Windows you had on (ie. Windows XP Home). So long as it's the same version, you don't need your own specific disc. It's the product key you need to activate it. In which case, it's likely easier to seek nearby computer stores or even shop online at Ebay.
If I'm wrong, try holding the Control key and continually tap F9. Start as soon as you turn on the power and continue until you hit the recovery screen. If you reach the Windows loading screen (the one right before the login screen), you went too far and that key combination didn't work.
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