ressurecting dead pc

My pc is an old dell with xpPro sp3, 4 mb ram, mucho hdd space.
Recently, it's not loading properly and can't get in to xp. It sits there with a light-blue screen with the cursor in the middle of the screen. The only acton I can do is Ctrl+Alt+Del to access the Task manager. I can reboot from here and as it's loading I can do F12 or F8.
I can access a Safe Mode load (various methods) or access the Utility Partition.
The last time I checked, the C drive was ok.
What is the best way to get the pc loading correctly?
One time (I don't know how I got there) I had the ability to restore the os to a previous sav, which didn't work. How to get to that ability again?
When it's running ok it takes minutes to shut down the os as well as many moons to reboot from a pc off situation.

 

do you have a slipstreamed cd with xpsp3?

if so you can do a repair install

you can also burn a copy of hiren's boot cd to boot into your drive to check which programs are slowing the reboot/shutdown process

you can also use the recovery console to reset os to a previous point using system restore

you should also use a rescue cd from kaspersky or avast that you can burn to a cd, and run a scan of the drive as your prob may be from malware.

can give instructions on burning a cd with the rec console and hiren's boot cd if you want to do these steps

with hiren's you can run checkdisk, and view event viewer to see what errors are being generated.