Have you tried another anti virus program like Avast? download this: http://avast.com/eng/download-avast-home.html
That is the free version of avast, once you have downloaded it, it will ask if you want to do a boot-up scan or something along those lines, i cannot remember if it updates or not but if you are unsure click restart later, then open up the avast program and click the arrow, then click updating then click iAVS which will download updates. Once that has finished then restart your computer and it should start up the boot-up scan, this scan could take a while and you cannot do anything on your computer while it is scanning, if it finds a virus it will ask you if you want to move it to quarantine or delete it completely, i normally click delete completely so it gets rid of the virus. If the boot-up scan does no load then once your computer has started up again open avast, click the arrow click Schedule boot-time scan and then click schedule, then restart and it should do it.
You can also try:
an online scanner like the one below:
http://onecare.live.com/site/en-gb/default.htm
Click the protection scan as you are just looking for viruses at this moment.
Perhaps a spyware program will pick it up like
Ad-Aware 2008 Free Edition from Lavasoft:
http://www.pcworld.com/downloads/file/fid,7423-order,4-page,1/description.html
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Chicken