Spent over an hour reading the stickys and similar threads - hope you guys can help me with this problem. Short Story: Sys was running Win 7 Ultimate (x64) - BSOD like crazy after three months. Bad memory stick, HD, and MB replaced - no go. Installed Windows XP Pro (x86) works fine. Install Win 7 anything (x86) on top of XP Pro - works fine. Try Win 7 by itself, BSOD. Makes no sense... Long Version: Custom built pc (by me - first time). Worked great for 3 months. Then one day it started random BSOD. After three days of that the system stopped booting. Pulled it apart, found a bad mem stick - one of the gold leads was burned (removed that stick and matching one - sys was 8gb, now 4gb). System boots, but BSOD every 15 to 45 seconds. Downloaded Ultimate Boot Disk and ran every test possible - all passed. Checked HD for errors on my old Dell system - nothing. Debug/Wiped the HD and tried recovering from back-up image on external HD - loaded fine, but then BSOD returned after 5 minutes. Wiped HD again, reloaded Win 7 Ultimate x64. BSOD during install. Swapped HD, same problem. Swapped MB and memory - went from Asus to Gigabyte, same problem. Tried loading Win 7 Home Premium N (x64) - same problem. Tried loading Win 7 Pro VL build (x64) same problem. OS crashes on install - gotta be hardware.. BUT.... I have an MSDN License so figured, what if I load Win XP Pro. It works - runs great. Then I decided to upgrade to Win 7 Ultimate (x64) - BSOD returns. Start over again, Win XP Pro runs great - upgrade to Win 7 Home Premium (x86) still runs great. BUT, i want a 64bit OS... Try clean installs of 64bit Win 7 Home Premium, Ultimate, and Pro VL build - all do the same thing - BSOD during or right after first run from install. Any clues? I would think hardware, but the system is passing tests and running Win XP and Win7 if installed a certain way. Damaged processor, maybe? 32bit OS not taxing enough to make the processor problem show up? Stuck on this one - any ideas are highly welcomed at this point. Side note - the BSOD errors are random, but the most common one is Cache. Get it about every 4th BSOD. Could not find disk caching options in Bios for either MB.