I have been working on an HP desktop computer with Windows XP that was shutting down on it's on during use and had gotten to the point where it wouldn't even boot into Windows because it was stuck in an infinate loop of choosing "last known good configuration" or "normal startup." I took the computer to my house and fixed the endless loop with a chkdsk /r and the computer seemed to be working perfectly. I left it on for a long time, played a video on Hulu, upgraded the antivirus program, and noticed no problems on the computer. I returned the computer to it's owner and she called me saying that the computer was turning off again after getting very loud. This sounds like a heatsink or fan problem to me, but I do not understand why the computer would work perfectly at my house and then stop working at hers. Also, before she was complaining of a clicking noise and said that she could only get the computer to work when it was on its side which does not seem as much like a heatsink problem. I'm trying to determine if replacing the heatsink is worth it or if I should recommend a new computer. The computer has a dual-core processor and a gig of ram. Thank you for your help!