I recently turned on my windows xp comupter, and within a few seconds a black and white screen came up which had much writing and at the bottom it said "disk boot error, insert system disk and press enter". I tried using my windows xp disk, and I chose the repair mode. It then came up with a choice of things such as bootfix etc. none of which actually worked. I have a lot of important documents on my computer, and I have not recently installed any hardware or software. Please help ASAP.

First...do not post the same thing multiple times. You posted this exact thing just two posts below this one. Make sure all your cables are in place and weren't accidentally disconnected or knocked loose. Make sure the Master/Slave Jumpers are set correctly. CMOS battery could be dead. Yes...this will actually cause that problem every now and then. BIOS could have lost the settings. Enter the BIOS and try to redetect the hard drives in the BIOS, or put detection mode to "Automatic." -=Bryan=-

Brian, use your XP system disk to boot. The first screen asks you if you want to install or repair, choose Install. One or two screens later it will again ask you if you want to fresh install or repair and installation. Now choos Repair and follow the prompts. This will reinstall XP, and hopefully will not overwrite your data fils.