If a Windows-based computer is stuck in an infinite reboot loop, as an IT professional, you must understand why...
it is happening and how to stop it.
The Windows boot 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.
How to solve the Windows boot 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, Windows' 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, you must edit the registry on the machine.
Go to HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlCrashControl, and either create or edit a DWORD named AutoReboot and set it to 0.
The 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. If Safe Mode doesn't work, however, 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 -- by mounting it in an external drive enclosure, for example -- and then use RegEdit or another utility to change the AutoReboot value.
Or, you can use a utility such as the Offline NT Password & Registry Editor, which you can boot -- and use -- directly on the target system without actually booting Windows.
Note any crash messages once auto-reboot is disabled. The blue screen of death (BSOD) usually isn't a welcoming sign. But when you're dealing with a Windows boot loop, it's better than another reboot.
The messages on the screen are instrumental in determining what went wrong and why. If you can reboot from a crash into Safe Mode, there are tools you can use to examine the crash information and diagnose it further. Microsoft has its own tools, but other options include NirSoft's BlueScreenView freeware, which does all the heavy lifting and presents a concise report of all the BSODs the system recorded.
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 reinitializes the system components. You should only use this option if everything else fails.
Windows 10 reboot loop options
As with any other Windows installation, a continually restarting Windows 10 operating system exhibits the same familiar BSOD. It may also display a message such as Internal Power Error, with similar problems. Even if you upgrade to Windows 10 on top of Windows 7, 8 or 8.1, the Windows boot loop conundrum is an ever-present possibility.
One Microsoft fix provides an update to correct this. The procedure is:
Open Settings > Update & security > Windows Update
Click on Check for updates and a further update, then repair the Windows boot loop issue. To prevent Windows 10 persisting in a computer reboot loop, make sure you have the correct drivers and that they are compatible with the operating system.
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