That's so overkill it's not even funny! I don't know what Joe Public does with his machine which makes him so prone to viruses, but this laptop sits on the kitchen worktop, switched on 24/7, with a public IP address. It has 4 important programs installed:
AVG antivirus (which has never been triggered)
Firefox (with adblock extension)
Thunderbird (for email)
Windows Firewall
No viruses. Not 1, ever. If you really must flatten your machine every 3 months, can I suggest using an imaging tool such as Drive Image, Ghost, or Partimage (free)? Another alternative for the paranoid is using something like Tripwire, which essentially checksums all the files on your disc, allowing you to verify their integrity at any time in order to check for modification. Also, the assertion that viruses are only interested in Windows components is incorrect.