I have a Windows-based computer stuck in an infinite reboot loop. Why does this happen, and how do I keep it from continuing?
The reboot 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.
There are several steps that can be taken to solve the reboot loop problem.
Attempt to boot in Safe Mode.
If you can boot the system properly in Safe Mode (press F8 at startup), there's a good chance whatever is wrong revolves around a device driver. Safe Mode loads its own set of fail-safe drivers, which are minimally functional, but more importantly, stable.
Disable the auto-reboot function.
By default, the Windows's automatic reboot-on-crash function is enabled on many systems, and this is likely contributing to the problem by not allowing you to see an actual crash screen. To disable the feature, the registry on the machine needs to be edited.
Go to HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlCrashControl, and either create or edit a DWORD named AutoReboot, and set it to 0.
But there's a catch-22: You can't edit the registry without booting the system. If you can boot to Safe Mode as discussed above, then you're set. However, if Safe Mode doesn't work, you have to do an end-run around Windows and edit the registry offline.
There are several ways to do this. You can attach the system drive to another computer (e.g., by mounting it in an external drive enclosure), and then use RegEdit or another utility to change the AutoReboot value.
Or you can also use a utility like the Offline NT Password & Registry Editor, which you can boot -- and use -- directly on the target system without actually booting Windows itself.
Note any crash messages once auto-reboot is disabled.
The blue screen of death (BSOD), as we've come to not-so-fondly know it, usually isn't the welcoming sign, but when you're dealing with a reboot loop, it's better to see that than another reboot. The messages on the screen are instrumental in determining what went wrong and why.
If you can reboot from such a crash into Safe Mode, there are tools available to help examine the crash information and diagnose it further. Microsoft has its own tools, but I recommend NirSoft's BlueScreenView freeware, which does all the heavy lifting and presents a concise report of all the BSODs recorded in the system.
Consider swapping hardware if there's no BSOD.
If reboot-on-crash is disabled and the system simply reboots without crashing, there may be something more serious going on. One culprit could be bad memory. Run a copy of Memtest86+ on the offending computer overnight to make sure everything is solid.
Attempt an in-place repair or a fresh install.
An in-place repair -- installing a copy of Windows on top of another copy --preserves the applications and user settings, but it re-initializes the system components afresh. This option should only be used if everything else fails.
Note that Windows Vista and Windows 7 have experienced far fewer incidents of the reboot-loop problem than Windows XP, possibly because of how things have been reworked in the new operating systems.
ABOUT THE AUTHOR
Serdar Yegulalp has been writing about computers and information technology for more than 15 years for a variety of publications, including InformationWeek and Windows Magazine.
This was first published in February 2010