A friend of mine's computer had a failing hard drive. So, I bought a new hard drive to install for him and when I plugged it into his computer I get the Non-system disk or disk error. hit key to continue. So i tried the hard drive in my own computer and it works perfectly fine. Every single thing I try to boot the computer from gives the same error. Windows XP disc, WIndows 7 disc, WIndows xp flash and windows 7 flash. I have changed the boot order correctly each time I try a different method. I have reset bios to default and disabled the network boot because that gives me an error of checking media cables. I am at wits end and if anyone with a similar problem could help me diagnose the problem that would be greatly appreciated.