Recently my computer decided to start locking up seemingly at random. Very rarely it will reset itself (and then lock up just before/after POST). It seems to be proportional to time since being turned on/locking up last in some cases but not in others. No new hardware added. No new bios updates. All devices within stock/suggested settings: no overclocking, no overvoltage, no tighter timings, I even reset the bios settings). No new software (not to mention it locks up sometimes before it even launches the drive and even as early on as graphics card splashscreen/test although I can get a blinking "cursor" when that happens, I tried without one and I booted from a livecd) I cleaned the dust (there was a bit but nothing major). I pulled it apart, cleaned it all and put it back together. No effect. I redid the thermal paste (and it dropped about 20 degrees from the running temp but it was fine before it). It then ran for just under 2 hours and locked up again. Temperature was well within limits for the entire time. I tried without drive and booting from CD. I removed as much as I could (1 stick of ram, only one graphics card, no hdds, no DVD drive, no wireless, all USB, sound and firewire removed bar the built in ones, only a keyboard attached: still locked when I watching the BIOS clock tick over). I do not think it is my PSU on the fritz, if necessary I will pull it apart and test it properly but it does not seem likely. I discharged the capacitors I could see (shorted terminals), it ran OK for a while but as it seems random I am not willing to draw any conclusions. In conclusion My thoughts were heat: nothing appears to be warm to senses or IR of the crappy camcorder I have. Cleaned and redone thermal paste, airflow is as good, if not better than it has ever been after the rebuild. Not to mention timing is very odd: thermodynamically stuff should not be able to overheat and cool and overheat again at the rates I am seeing. Connections all appear fine and I did do a strip down and rebuild. My next thoughts were dead capacitor: I have not tested them all yet but they seem to be working, most just seem to be signal smoothing based as well and lockups are too random for it to be that. Unfortunately I lack the equipment to test each part (the other problem with high end machines), the only people I know with capable stuff are out of the country and PC shops are either PC world (£50 for walking through the door and I would be willing to bet my problem is "spyware" and the only solution a £100 set of AV software) or independents who I trust even less than most politicians ("your machine is broken but I have a state of the art 386 you can have for a £1000"), are incompetent (they gained their skills at PC World you know) or are those who are out of the country Edit: my specs: http://gbatemp.net/index.php?showtopic=428...t=0&start=0 I have a different CD drive a a crappy wireless card I salvaged (it has been working for about a year now though). My machine has been well (ab)used since I built it so I would not be too shocked if parts are dying but I would rather not have to get new stuff, especially if I am overlooking something obvious.