Ok, time for a quick reply before attempting round 3 of digging out my works van from the snow then digging out the street...again.
post :- (power on self test) is a small bios program that makes sure your keyboard,ram, disk drives, graphics cards are there before starting up. if all is well, the computer begins to boot.
in response to your replies, try to find out the make/manufacturer of the hdd and see if theres a hdd test program. i've had a few failures of hdd in my time but to be honest you usually see them coming before the thing fails completely. (hdd making excessive noise, slowing down, sluggish etc)
I would think that xp or the hdd mbr may be at fault here and a simple repair of the files or repairing the mbr might do the trick. If the MBR (master boot record) is corrupt on your hdd,your pc won't know what to do with the hdd and you'll be presented with a blank screen. (recovery console can repair the mbr, (access this using a copy of xp and entering the recovery console from there) but backing up your data might be best first)
try googling xp recovery console for a few hints and tips and how to's. spend a little time reading up on it and you'll pay dividends later.
the recovery disks you mention will contain all you need to reinstall xp and all the drivers specific to yer mates pc but beware...some of these recovery disks wipe the hdd and start from fresh. if things get as bad as this, back up anything you cannot lose before starting.
try downloading and burning a copy of hirens boot cd (version12 is the latest i think). this (free) cd contains loads of programs and diagnostics stuff to help fault find/repair. if your not sure what a program does, google it.
best of luck.
Bolty.