I would try using the recovery CD first. Are you changing the motherboard or just the CPU? If that fails, your next choice is a new copy of XP, or switch to Linux.
It won't hurt to try the card again. If the symptom reappears, you can assume the card or the port is bad. Turning off the machine is one of those controversial topics that comes up often. You can save some power that way, and some wear, but turning off and on also introduces some wear. Check your Power options in Control Panel, and look at things like turning off the HDs and the monitor, but overall a decent computer just doesn't care that much.
As far as I know, you can't install AVG in safe mode-some services cannot start. Did you do a full format on the correct partition? I agree with you-this should not be a problem with RAM or MOBO. I've installed with missing files before, and it might be worth trying.
First, double check that everything is installed properly-RAM seated properly, all cards and cables tight. If OK, remove the power plug and turn off PS switch if you have one. Hold the Power On switch in for 10-15 seconds. Re-connect and try to boot.
Is the proper printer selected in the File/Print dialog? Can you uninstall the printer? Do so, if possible, then reinstall it. Use safe mode if necessary to remove the printer.
You really need to see this error message. In the past, I have done this by holding my finger over the "pause" key and pressing it quickly when the message appears. If it's really quick, you need to anticipate its appearance. This will work if you're patient enough. If you really don't know how to get the files off the computer before re-installing, or how to boot to a recovery scenario, you should probably abandon this project. I say this because it's her boss's computer, and the result of a loss of data could have dire consequences.
