Hi,sloane

First have a look here it maybe why this happen.
http://www.microsoft.com/technet/sec.../MS03-011.mspx

To help remove it look here.
http://www.trendmicro.com/vinfo/viru...R%2EA&VSect=Sn

Now download this prog here to help remove all of Mca

Registry Mechanic
http://www.pctools.com/registry-mechanic/

Till us if this was any help to you.

HGD