Hi all. I've recently upgraded from Windows 7 to 8.1 and since then started getting BSOD screens after every startup (approx. 1-2 minutes after I go to Desktop). It only happens after the computer has been completely turned off and then started again, i.e. I don't get BSOD screens if I restart the PC. The error messages are different every time. So far, I've had about 30 of them: System_Thread_Exception_Not_Handles, Driver_Verified_Detected_Violation, NTFS_File_System, System_Service_Exception, Memory_Management, Attempted_Execute_Of_Noexecute_Memory, PFN_List_Corrupt, Bad_Pool_Header, etc. etc.).
After the computer restarts by itself, I get a black screen and have to reset it manually. After that, everything is fine until the next shutdown and startup. In the last few weeks, I've updated all my drivers, run a dozen diagnostic tools plus tried solving each error message with forum suggestions. Nothing helped! Would really appreciate any help with the above issue.
CPU: AMD FX-6100, 3600 MHz
MB: Asus Sabertooth 990FX R2.0
RAM: 4 GB DDR3-1333
Graphics: AMD Radeon HD 7700 Series (1 GB)
HDD: Seagate Barracuda ST2000DM001 (2TB, 7200 RPM, SATA-III)
BIOS: AMI (09/16/2013)