At the end of last month I bought a new computer and for some reason it will not stay shut down. I started the system on Vista, but switched to Windows 7 RC at a friend's recommendation and have the problem on both OS's. To elucidate, when I go to Shut Down the computer turns itself off normally, then after perhaps 3 seconds the fans will kick back on, usually for a second or two, shut down, and then a couple seconds later will turn on again and the entire system will boot itself up. Likewise, if I tell the computer to Sleep, it will go into Sleep mode, but the fans will kick on, run for a few seconds, switch off and stay off for a few seconds, then turn back on, turn back off, over and over and over again infinitely as far as I can tell until the power switch to the supply in the back is flicked. I cannot turn the computer back on from Sleep mode (with mouse, keyboard or power button on the tower), by the way, while it's doing that. I have to cut the power and turn it back on from there. I have looked up this problem in many other forums and have seen solutions such as disabling all reboot effects in the BIOS (which I have done to no effect), unplugging all of the front tower buttons from the motherboard (no effect), and also wiping the hard drive in case of some sort of faulty installation—also, much to my chagrin, to no effect. My hardware follows: GIGABYTE GA-EP43-UD3L LGA 775 Intel P43 ATX Intel Motherboard SIGMA ZEN ZEN-WDP diamond pink SECC Steel ATX Mid Tower Computer Case Thermaltake Purepower W0100RU 500W ATX 12V 2.0 Power Supply EVGA 896-P3-1255-AR GeForce GTX 260 Core 216 896MB 448-bit GDDR3 PCI Express 2.0 x16 HDCP Ready SLI Supported Video Card G.SKILL 4GB (2 x 2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory Model F2-8500CL5D-4GBPK Intel Core 2 Quad Q8200 2.33GHz LGA 775 95W Quad-Core Processor Model BX80580Q8200 As for my HDD and DVD drive, I'm not sure. I believe the HDD is a Western Digital; about three years old, 250GB, 7200rpm with 8MB cache. Both these drives were in my old computer and were just moved into the new one to save money. I hope this doesn't seem uselessly verbose, but I wanted to try to be specific and I would like to find out why my computer is behaving this way.