I have W7 on a laptop. It freezes 10-60 min after startup, even if no programs are started. Same problem if I startup in safe mode. After freezing, sometimes the blue screen appears, sometimes the screen just goes black. The computer restarts, then after some minutes comes to a halt with "no operating system found". It restarts nicely after shutting off the Power, and I can start Windows normally.
I tried System Restore initially, but Windows could nor finalize this due to an unknown error. Have tried changing the memory, same freeze problem.
First the mouse pointer will freeze in one program, then go to the round circle. No specific program or task that precipitates the freeze. Sometimes another program will work for a short while. I cannot start Task Manager. Caps Lock and Num Lock will work for a minute or so, then the whole computer freezes.
Any ideas appreciated!