<Try running your scanner while in Safe Mode (press & hold F5 or shift at Windows start-up).

If this fails, jot down the names and locations of all the files that are backdoor programs. (e.g. C:\Windows\system\quicken.exe).

Reboot. Press F8 just after the BIOS screen disappears (you can repeatedly tap F8 to make sure you get it). You'll see the Windows boot menu. Choose "safe mode command prompt only". You will be placed at the C:\> prompt.

Delete each file ("del filename") by navigating to its folder (using "cd foldername" and "cd .." to go up a level). If DOS says it can't find it or it's locked, then you will need to change the file's attributes. Just do "attrib -s -h -r filename" to remove the System, Hidden, and Read Only tags all in one shot. You should then be able to delete the file.

When are all deleted, reboot. Windows may complain that files it's supposed to run at startup are missing. Use msconfig to edit the bootup system and remove the virus files from the "start these when loading" list.