This is not a feature in Windows XP (as far as I know). You can add
this feature if if your machine is part of a domain network (which I
assume you don't have and is out of the question for you). I suspect
(but not sure since I don't have this product) that Norton Internet
Security using Parental Controls features will permit this. See http://www.symantec.com/sabu/nis/nis_pe/features.html Surely there are
other 3rd party products that you can buy, and perhaps some that are
free for download.