Ok so my friend brought me his computer because it stopped working.. ive been trying to fix it but i believe his motherboard my have gone out.. because when i go to start up the computer it will load up the first screen which is the motherboards name on it and it wont go past that part.. also he said that when it broke, his brother unhooked the wrong HDD and the one he unhooked was the main one which had windows and after that happen it never worked again.. any help would be greatly appreciated.. and ill try to answer any questions that you might have to helping me fix his computer..
First try using a linux livecd (gparted is a small one), see if that works. The linux livecd will bootup the computer without installing on the hard drive. This will let you see if you have a software or hardware problem. Also see if it acts the same with a different hard drive. If this was a dualboot, it could affect things if the drive wasn't place back in the correct position. If it's xp, you can use the free paragon rescue kit 9.0 express bootcd to fix drive letters/boot.ini.
The_Slash, disconnect all cables to drives, reseat all ram & cards. see if can get into bios with no problems. if that works then reconnect 1 power & 1 data cable to a drive to see what happens & repeat that process till all connected & working. can also clear the cmos so it goes back to default settings.