anti virus needed!!

Ok..help me out or am I screwed with my Pc at home?

I got a stupid pop up msg about a Malware virus!
I got Windows Xp Service Pack 2... and the pop up appears usually where the anti virus symbol is next to the time at the bottom.

But I cant double click on it or right click..
The symbol flashes red alert on and off :(

I think by memory thats how u spell it..
Can I get rid of this meanie?

If so..how?

Thanx