I just cleaned the Sirefef trojan off of my fiance's notebook. Microsft Security Essentials (which is actually pretty good and free) could spot it, but it was unable to actually remove the stupid thing. It was residing in a folder that was masked from Explorer and the command prompt too (not a "hidden" folder either, this was something deeper). I ended up using a Linux boot-cd to mount the drive from the outside where the folder was visible and then I nuked it from orbit.. it was the only way to be sure.
I know that my fiance downloaded & installed the malware back on the 2nd... hopefully I'm done with this crap for a while. There's a reason I use Linux whenever I have the choice