Well after a lil google work and speaking to the IT guy here at work we've come up with several things: -
If you have Win98 then you can reinstall quite easily without having to reformat. Hopefully the installation CAB files would be in somewhere like Windows/options/cabs, which you then move/copy to a folder not inside the windows directory on C: drive. If they aren't there then copy everything off the Win98 installation CD into a folder on C:. You also want to copy any drivers or similar that you might need back. Next step is to reboot into DOS mode, and rename the Windows and Program Files (called progra~1 in DOS) folders to something else. You can delete them after you've reinstalled successfully. They go into the Win98 cabs folder, and run setup. That'll reinstall Windows from scratch without having to reformat. Make sure you reinstall into a new Windows directory, not the renamed version. Alternatively if you have a second partition on your HDD called D or something then copy all your data into that (if you have a big disk, then always create at least 2 partitions for this reason - one for OS and one for data, so you can blow away the OS from time to time as a routine). You can then reformat C if you want without losing data.
For XP you probably want to boot off the installation CD and try the various recovery options there. If you get no joy, and the disk is NTFS then you may have to reinstall. You can try without formatting but it may not work, and booting with a DOS disk won't help as it wont read NTFS partitions. Using a Knoppix live linux CD would be your best bet here to access the hard drive and back up your data first. Got one you can copy if you need it.
Hope that helps - remember Google is your friend?
also
I came acrross something called a switch - you get into comand prompt and type setup /p i as far as I know it stops the computer lookin for plug and play devices, as I got the error after my resolution changed on its own I'm thinking maybe the gfx card maybe the problem.
Also another suggestion is to: -
Try this: go into DOS mode by holding the CTRL key down, and when you get the menu, select "DOS Prompt only". when it comes up in DOS, type this:
SCANREG/RESTORE
Do you have a spare GFX card? Or check original is seated properly - AGP ports can be a bit prone to working loose I think.
Basicly before the error my resalution decided to change on me after running mohaa the START button took up the whole screen so maybe my gfx card is screwed
