Do you have Windows Xp Service Pack 2? If not, you need to download it. When/if you do, make sure you have the Windows Firewall set on as some measure of defense for your computer that if I read correctly, lost it's firewall.
I think it would be helpful for the people here if you also posted what kind of unexpected/new things you have noticed in the edit/remove programs list that you mentioned. Also, you said wierd things are happening, were you referring to the aforementioned programs list?
Next, head to http://housecall.trendmicro.com/ and get a free viruscan. That should get you started until a real expert gets in here.