I'm pretty sure we can get you up and running again. The first thing I would do is a SFC from the command line
To do this simply go to the Run box on the Start Menu and type in:
"sfc /scannow" without the quote's this will check your system files and replace them if any are missing etc. You might need your XP disc if your I386 folder is not on your hard drive.
Hopefully that should sort your problems out.
If not you could do a system repair with you XP cd, with a repair you should not loose any of your data but I would back up as a precaution.
Hope this Helps Kindest Regards Tony B.