I also recommend doing a full system scan using Microsoft AntiSpyware after
removal. Restart in safe mode. On the Scan Page, choose Scan Options > Full
System Scan.
If this keeps coming back, there's a great little tool
called BHODemon that can take care of it. BHO's are
browser helper objects - things that IE thinks it needs to
run. You can manually turn these things off, and they'll
never come back to bother you!