1. Cold start machine and boot/scan with AVG Rescue Disk. Update program and virus def first with an internet connection.
  2. Reboot - run windows
  3. Run Superantispyware
  4. Download AVG Internet Security, install and run root kit scan

Some Malware will change the registry so that AVG does not install or run. Runing SuperantiSpyware Portable can help to clean the registry.

If AVG comes up with... 

"This operation has been cancelled due to restrictions in effect on this computer. Please contact your system administrator."

check the registry... HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer\DisallowRun for applications that have been turned off.

If AVG was installed previously, you may need to run the AVG cleaners to fully remove it.

AVG free will not fully protect your PC. It does a reasonable job - but it doesn't protect you from root-kits. You'll need to buy the full version of AVG for better protection.

Other Tips

Backup your PC regularly! If you catch a virus, you can then restore your machine with your backups.

If you don't do a full backup - at least backup your registry and personal photos and files.

Make sure your system restore is on. Don't delete them (as some people do) as they can be used to restore your registry.