Morning Fbat. Uploaded latest Nvidia drivers last night and left it downloading a lot of Win 7 updates overnight. checked again this morning and PC was frozen. Powered off/on and tried to get into Safe Mode but it froze as it was listing the loading files. Tried to get into Win normal mode and again froze on startup.
I think I have replaced everything except the Mboard & processor but have never heard of either of them causing this problem.
I think it is unlikely to be a driver issue and it is more than possible to be a motherboard fault or CPU for that matter as this will need to be processing information as soon as you press the power on button.
If the instructions from the CPU are having trouble getting to the various components then this will cause the problem you describe. Equally if the CPU is having trouble processing information and sending out instructions then again the issue can occur.
If you have a spare CPU then installing this would pretty much tell you which component is at fault.