What measures do I take up after I scan my pc for viruses?

Ok, I know I have a virus in my pc cause my anti-virus expired. I bought a new one did a system scan cleaned up 12 adware and p2pnetwork viruses got rid of them but some how I feel like I still have one lingering in my pc still infecting it, like a downloader.

I ran full system scan and it does not find the infection but I know its there because I can no longer delete programs from the add/delete program lists.

What is my next step? Will a full system restore fix this problem? I know I will lose most of my data but I want to know if doing that will be a sure fix.

I also get a window from ''HP'' saying that I need to update a certificate so that my pc can download up to date software. the certificate looks like someone scanned it and paste and the exp date on the certification is mar 2005. that happens everytime I start the pc. Which I keep declining.

What measures do I take up after I scan my pc for viruses?mcaffee

there's a possibility that what you have is not not a virus but a spyware/trojan/adware that explains why your anti-virus can't locate nor delete it. if you have an anti-spyware run it and check if it finds anything. if you don't have it, here's a free one: http://www.2-spyware.com/review-spybot-s...

the simpler way is to re-install windows, it always help, but i guess you want to same your data.

What measures do I take up after I scan my pc for viruses?norton antivirus 2007