Re: Hand back the geek ID card, return the butter knife and leave
When faced with a sick Windows box, my steps are:
1) Open it and hoover out dust & crap, then check for Bulging Capacitors Of Death on the motherboard.
2) Boot a Linux CD/USB (old PCs often wont boot from USB happily so CD/DVD needed) and run the memory tester.
3) Check the HDD SMART status to see if its dying.
4) Boot a BitDefender or Kaspersky "rescue CD" and check for root kits and lesser malware.
If all of the above pass, then you know its 'just' a simple problem. But for most PCs not looked after by a competent Windows admin, you know its going to have so much crap installed and partly uninstalled that saving the data and nuking from orbit is the best solution.
That is, assuming they have the original Windows disk / rescue disk they were told to make when the PC was new...