Hard though it may be to imagine, even after going to all of the trouble to switch to Windows XP, you may pine for the old days. Some people find Windows XP too intrusive and too much of a nag. Other people find too many incompatibilities with their old gear. Fortunately, Microsoft has made it very easy for you to back out, reinstating your older operating system.
This option is available only if you upgraded your PC from Windows 98, Windows 98 SE, or Windows Me. If you erased the hard drive and performed a clean install, or if you upgraded from Windows NT 4.0 or Windows 2000, this option isn’t available. Furthermore, you lose this option if you repartitioned your drive, or converted it to NTFS, since you upgraded.