Sons laptop not booting

Hello,
Been awhile since I've been on here (luckily, if you know what I mean!). Anyway, two days ago, my stepsons laptop (FOR COLLEGE!) just went haywire. It will start to boot up like nothing is wrong....but then it restarts again....and again.....and again, etc. It will boot into BIOS and I can make changes in there, but when I exit...same thing! I've tried using a windows disk to repair, but it says that there is no hard drive detected. HP support says that it is the motherboard (this would be the SECOND TIME in just over a year), but that it is "out of warranty", and they refuse to replace it!

Ok, so what he has is this: HP Pavillion DV6119US
AMD Turion 64 X2 1600Mhz
1024 mb memory
Seagate hdd....thinks its a 80gb
Windows XP Media Center

Any help would be greatly appreciated, though I don't know if anything can be done. He is returning to college in a week and NEEDS his laptop! Please help if you can....I know you guys are the best! Thanks in advance!