What version of VirusScan, Home or Enterprise? No antivirus is guaranteed to catch everything unfortunately. I ask because you posted in a general section originally and I moved it provisionally to the home user section.
The best way to avoid these things is to be ultra careful using the Internet, and when downloading and keeping Windows totally up to date plus a few other tools in standby as mentioned below.
Try using System Restore to go back to before this happened but if successful don't forget to update Windows and your virus protection right afterwards.
If nothing works in regular mode you can initiate that in Safe Mode.
I also suggest using a few extra tools such as Stinger and Malwarebytes Free - see this document for suggestions and links to them: https://community.mcafee.com/docs/DOC-2168