fix computer errors

I recently got a blue error message. I believe it was the Blue Screen Of Death (not the “Windows has encountered an error and will be shut down” message), and these are the specifics it gives me:
DRIVER_IRQL_NOT_LESS_OR_EQUAL
(and here are the hex addresses it give me under technical information)
*** STOP: 0×000000D1 (0×00000018,0×00000002,0×00000000,0×0xF8…
*** iastor.sys – Address F813125D base at F8122000, DateStamp 422f3bcc
I know a few things about computers. I have a somewhat understanding of how hex works, and those hex values look like addresses. I believe they are literally the source of the problem. I believe my computer was accidentally shut down mid-update, or there might have been a program or driver (or possibly even a virus) that could have interfered with a Windows update and caused it to shut down without finishing said update. Also, I can’t start Safe Mode, I get a string of messages that read like this:
multi(0)disk(0)rdisk(0)partition(1)\WI… sys driver here*
It stops with the sys driver on agpCPQ.sys.
In other words, Windows won’t even start up. I know the operating system still exists on the computer because the logo pops up when I try to boot it normally. Plus, system restore doesn’t work; it just restarts my computer.
If anybody can tell me a possible way to fix this problem it would be wonderful. I do have two computers (both running XP) but I’m working on my masters degree and all my homework is on the broken computer. Its all due in just two days so I need help immediately!
Remember, I have two computers both running XP, so if there is a way I can use my working computer to fix my broken one then include that in your answer please. Thank you.
(Closing note, I don’t have the start-up disc.)