This forum is reserved for feedback concerning the forums themselves. Your question would be best addressed in the Windows XP forum.
In regards to the question itself, there is no simple answer. The problem is that without the certificate of authenticity, original Windows CDs, etc you don't really have a basis for arguing its legitimacy to Microsoft. You could go here for the 'official' validation page, but if your copy turns out to be invalid you're left with either purchasing a legal license to Windows or choosing a free Linux distro such as Ubuntu.
Please help! A friend bought me a Computer at a yard sale this year and I'm dissabled so it's been a great lifesaver .Anyhow I got online a month ago and went to Microsoft download and was doing some much needed updates when I wanted to update to XP SP2 from SP1, and it told me "This copy did not pass genuine validation" . I didn;t purchase,and can't afford to purchace any software for this computer.So can someone please tell me what I can do to validate so I can proceed with the other much needed updates I need. Thank you for your time and help.