If you don't want to download anything, run this online virus scanner. It has worked for me in the past.
http://housecall.trendmicro.com/
Be sure to run it in IE though, it won't work on Firefox if I'm correct. It's a good scanner, whatever you can't remove you can find a special program to remove a specific trojan/virus/worm that Trend Micro will detect.
From the anti virus scanner suggested above, go with Avast, I've never used Avira but Avast constantly updates and its been good for me. AVG is overrated.