Seems to me you don't have much time to try troubleshooting so-
First try unplugging EVERYTHING except the keyboard out.If windows boots in plug them back one at a time until you find the problem.if not-
1.Insert windows cd and boot to it
2.Select install windows xp(don't worry we're not doing a wipe)
3.Select "repair current installation" and pick your windows installation. It looks like a windows installation but don't panic,you're files are safe,it's just re-installing the System files.You're desktop will be wiped clean but the files are still in your hard drive,just search for them.Please don't install a new windows!!!This will wipe you're data if you do it on the same partition.
If this doesn't work get back to me and I'll bring you through installing a secondary OS or how to take out the HD and get the files if you don't have enough free space
This is (usually) the quick easy fix.There are a few less drastic measures we could try but I'm guessing you need those files for school on monday.If you have time to tinker and don't want to repair we can try something else