The initial sign that the computer will show problems on rebooting is that it simply restarts straight onto the Windows installation CD (that's left in the disk drive ready for the frequent bouts of problem and remedy, namely system restore).
The last loading display before desktop rather than leading to the desktop results in a lime green screen and error message whose details I can't remember. Computer rebooted and repaired with Windows installation CD, system restoring to 2 days previous.
Next day now and computer randomly restarts onto Windows installation CD as mentioned whilst running. Now however the drive is not always recognised to be repaired needing Shut down and reboot. The system repair does not work but now neither does the (now much missed) system restore. The display claiming that there are no previous restore points to use. Safe mode now leads to just a blank black screen as does starting normally, and as to add insult to injury the system repair seems to continue indefinitely (although I have yet to allow it to run much over an hour).
There most likely is a hardware issue with your system. Post your issue in an appropriate thread and provide details about it, e.g., motherboard, CPU, PSU, RAM, video card, etc. Also tell us if you are overclocking the CPU or memory.
If you have tried a repair of the installation and it is not working there may be a fault on the MOBO. I would need to know if the system has been OC as this is the main culprit for damage on MOBO's. Also run check disk for errors on the Hard disk.