I feel I must point out that malwarebytes detects and removes malware(adware,spyware,etc) and not viruses and trojans.
The best tools for malware removal are malwarebytes and spybot. For virus removal it's really up to you as long as it's not norton or mcafee. I wouldn't touch those two with a ten foot pole. In cases where an infection has already occured I highly reccomend "housecall" by trendmicro. It's free and requires no install. If you do all the scans and are still having trouble please do let us know. Oh, and we need to know what OS(2000,xp,vista,7) this is.
I own my own company and I literally do this stuff all day every day although most of the time people let their system get so bad it has to be wiped.
P.S. I usually use a linux livecd that has clamav on it to remove the bulk of viruses and malware first, but that may be beyond the average user's skillset. Linux ftw.
