I have a PC I built back in early 2008 that had run without any cooling issues for a solid 7 years before a few months ago when it started setting off the CPU temperature alarm. It happens when it starts running above 75C under high workload (usually video encoding). Even when just sitting idle on the BIOS screen looking at the CPU temperature it would hover around 55C-60C. I'm honestly not sure what it's normal running temperatures were when it was working fine because I had had no reason to check after the initial build before the alarm started going off. The case has two stock fans: 120mm outflow fan on the back next to the CPU and below the power supply, and one inflow 120mm at the front near the bottom blowing on the hard drives. The CPU used the stock cooler. The case has several improvised air filters that prevented a lot of dust intake and I have an electric blower that I used to clean it out thoroughly at least once a year, so it was kept reasonably clean. When the alarm first started going off I cleaned the computer out again, although it was not very dirty. When that didn't help after researching overheating I removed the stock cooler and made sure it was thoroughly clean (there was no hidden buildup of dust or anything.) I put the cooler back in (I did clean off the old thermal paste and apply fresh) but it seemed to make the overheating worse. The fan on the cooler seemed to be working fine too. When that didn't work I bought a new cooler (an Arctic Freezer 7 Pro) and installed that, but again the problem only seemed to get worse. It has never been overclocked, and the computer as a whole was never upgraded aside from adding a 2nd hard drive about 5 years ago, and a USB 3 miniPCI card + faceplate about 3 years ago. I have also never updated the BIOS. I DO use a UPS with the computer, but I tried plugging the computer directly into the wall and it still overheated, and a different computer plugged into the same UPS (not at the same time) did not overheat or trigger an alarm of any sort. Is this likely to be just due to the age of the components? I would very much appreciate any advice for diagnosing it further. I don't know much about diagnosing overheating. CPU: Intel Core 2 Quad CPU Q6600 @ 2.40GHz (ran on the stock cooler for 7 years; then replaced with Arctic Freezer 7 Pro ) Mobo: ABIT IP35 Pro RAM: 4GB RAM Video card: GeForce 8800 GTS Case: Cooler Master Mystique 632s mid-tower (both 120mm fans are the case stock fans; appear to be working as normal) PSU: PC Power and Cooling Silencer 610 EPS12V Misc: Pioneer DVD-RW drive, miniPCI USB 3 card + faceplate, 2x hard drives. OS: Ubuntu Linux now; Windows XP for the first 2-3 years of its life. Any help is appreciated. Thank you.