I am having this problem lately. When my computer is turned on, it starts normally then sometimes display doesn't show when going to the desktop (switch on, window logo appears, then the display disappears when getting into the "Logging in Window" part). I know that the CPU is running because when I press the CAPS LOCK in the keyboard it turns off and on - the light of the CAPS LOCK indicator and I can properly shut down the computer via ALT+F4 then enter (the CPU really shuts down normally - lights off after a few seconds of doing alt+f4 and enter). And my computer can run normally on safe mode (with normal display).
My Cable is well connected from the CPU to the Monitor. I am using Samsung SyncMaster PX2370.
My CPU has the following specs:
Intel i7 950 3.07Ghz
2GB RAM (the other 2GB RAM was busted so my computer now runs only one 2GB RAM)
Windows 7 Home 32bit