Machine keeps restarting
BEFORE / AFTER
The computer restart loop problem is often the result of a device driver, a bad system component or hardware that causes a Windows system to spontaneously reboot in the middle of the boot process. The end result is a machine that can never boot completely.
An in-place repair — installing a copy of Windows on top of another copy –preserves the applications and user settings, but it reinitializes the system components afresh. This option should only be used if everything else fails.
Note that Windows Vista and Windows 7 experienced far fewer computer restart complications as opposed to Windows XP reboot loop issues, possibly because of how things were reworked in those operating systems.