If you've used other applications to try and bypass the Windows 7 activation system and/or you've not uninstalled them before trying to use Windows Loader then 9 times out of 10 that's why you're not passing as genuine.
WAT Fix will:
Correct file permissions
Correct important system files
Correct services required for activation
Correct VBS file associations
Remove Microsoft entries from the HOSTS file
Run WAT Fix
Install Windows Loader
If required visit the following website to revalidate Windows:
(Use Internet Explorer)
Warning: Do not close WAT Fix while it's running.
If after running WAT Fix you're unable to boot then insert your Windows 7 DVD and restore your system by using a System Restore point. The bad news is you'll probably need to format to cure your activation problem if this happens.
Virus scanner results
All virus scanner detection's are a false-positive. Simply turn off your anti-virus while running the program.