Special Note:   Remember – If your computer appears to be infected the first step I perform is a Windows System Restore.  A system restore will return your computers system files to a state recorded on a particlulare date and time you have selected.

The longer the virus, malware, or scare-ware is running the more deeply it can embed itself into your computer, even disabling the ability to install antivirus / antimalware scanners.  When you perform a system restore the malicious files may still be on your computer but the modifications made by the virus that allows it to run when the computer starts up or the changes to critical system files will have be removed and restored.  You need to still need to scan your computer after the system restore with an updated Anti-virus and / or Malware scanner.

To perform a system restore:
Start / (all) Programs / Accessories / System Tools / System Restore. Restore your computer to an earlier date and time (when your computer was not infected).

Malwarebytes (free edition Scanner – Purchased version provide realtime protection)
I started using this little GEM of a scanner when some of my Favorite scanners failed to detect or remove nasty infection like the Vundo Virus, AntiVirus 2008/2009/360 and many others.  This scanner detects virus, malware, trojans, and other unwanted programs by how they behave, what they access, if they are monitoring keystrokes, spawning / creating / modifying exiting programs.  This is my favorite scanner -  1/2012.
Go to MalwareBytes.Org to download the free version or use this direct link – Download MalwareBytes.  If the previous download link does not work then you can click here to download directly from FileHippo.com

Super Antispyware scanner
Download the free version of SUPERAntispyware protection. The free utility is one of my favorite tools that I install to detect and remove malicious software.

ComboFIX
This free utility should only be downloaded from Bleepingcomputer.com as the author has authorized this as the only distribution source.  This powerful utility is included in my toolkit but should be used by experienced technicians (or desperate users).  The creator of this utility also warns that the utility should not be used without supervision or it could cause your computer to not operate correctly.

Panda Cloud antivirus and Malware Scanner -  Cloud based scanning does not require you to install the software but simply initiate the scan from within your web browser.  The utility make take a little longer but this type of scanner has the advantage of being able to scan your computers when the virus prevents the installation of traditional  removal tools.

Microsoft  Malicious Software removal tool -  Anti-Malware and Virus protection.  This tool continues to be updated by Microsoft and now include Botnet detection.

Norman Malware Cleaner – PC Magizone rated this scanner just below Malware Bytes by only a few points so it must be pretty good.