Recently, I got a virus. No, not physically, a computer virus. Thankfully, it was relatively benign, as computer bugs go, but getting rid of it was about as easy as getting rid of cockroaches. The bleedin' things'll survive just about anything. However, there's one thing I realized (or, should I say, remembered?) after running far too many spyware killers and anti-virus programs: On a computer, no simple software bug survives a low-level format c:. Hiding in some "good" file, or as an execute line in the registry? Tough to hide when such things get wiped out. Needless to say, it didn't take me long to execute the nuclear option on my hard disk drive.
So, that said, here's the decision: Since I can't guarantee that anti-virus software will be effective in the elimination of threats, nuking the HDD will become a semi-common thing. Further, in the interest of getting back up to speed quickly with such things as additional programs (Firefox, and other like things), install files for them will be kept on a known-clean external HDD (or possibly a flash drive) and used for installation after the wipes.
There you have it - a no-frills approach to computer security. AV software to find the bugs, format c: to sweep 'em away. Not exactly something I would suggest to the average user, but when it comes to the computer, I suppose it's safe to call me an extremist.