How to Secure Windows - Cleaning Up A Windows Install From Somebody Else
 

I'll assume you are securing Windows XP, since XP was Microsoft's primary consumer offering from 2001 to 2007. The tips in this article also apply to Windows 7 and Vista, but the examples are based on XP.

I assume that the copy of Windows you want to secure is on an "unknown computer." By this I mean a computer that is previously unknown to you, so you can not make any assumptions about it. If you're refurbishing a "known" computer, for example, an old machine you haul out of your own basement or attic, you may be able to skip some of the steps.

http://www.osnews.com/story/23768/How_to_Secure_Windows