To keep my reg cleaned and prevent spyware build up I use products from this site. I have had reg mech and spyware doc on both windows XP and Vista with no issues. I also like the real time protection of spyware, this seems more important then antivirus these days.
http://www.pctools.com/
Tom's Hardware should get you up to speed on PC components.
http://www.tomshardware.com/us/#redir