Hi. ive just recieved a desktop pc from my FRIEND and first time booting up showed the "DISK BOOT FAILURE, INSERT SYSTEM DISK AND PRESS ENTER" error. Not knowing MUCH about computers i opend the casing and gave the internals a good clean. The error message went straight away and normally booted but the loading screen logo was xp but the desktop was vista which i just forgot about thinking it wouldnt matter. but when the computer got to desktop NOTHING would work. ive tried usb keyboards usb mouses the keyboards and mouses what could be plugged into the motherboard green and purple slots (sorry i dont know much about computers) front usb ports back usbports nothing works. ive also noticed the MONITOR cable has to be plugged into the grapics card as the motherboard monitor slot doesnt work. any ideas?

not much i can tell you but it might help:
amd processor
512mb ram
120gb kingston hdd
unknown name graphics card but its 128mb
dvd drive

Help would be very appreciated!This is going to sound like a really crappy question, please don't be offended.

Did the PC work before your friend gave it to you?Give it backit SOUNDS like the motherboard is fried.