What you can do against the Windows boot loopTry to boot in safe mode. If you can boot the system in safe mode – press F8 at startup – chances are good that a device driver is causing the problem. In safe mode, Windows' own drivers are loaded, which offer only minimal functionality, but, and this is much more crucial, are stable.
Deactivate the automatic restart. By default, the Windows function to automatically reboot in case of a system error is enabled on many computers, which probably contributes to the problem, because you won't see the actual crash message. To disable the feature, you need to edit the registry of the PC in question.
Start the registry editor and navigate to
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\CrashControl.
Then create or edit a DWORD named AutoReboot and set its value to 0.
The dilemma: You cannot change the registry without booting the system. If you can boot into safe mode, as described above, this is not a problem. But if this does not work, you have to trick Windows and edit the registry offline.
This can be achieved in several ways. You can connect the system drive to another computer – for example by mounting it in an external drive enclosure -. Then use RegEdit or another tool to change the value of AutoReboot.
But you can also use a tool like the Offline NT Password& Use Registry Editor, which you can boot and use directly on the target system without having to start Windows for this purpose.
Make a note of all crash messages after disabling automatic restart. The Blue Screen of Death (BSOD) is usually an unwanted sign. But if you're dealing with a Windows boot loop, BSOD is better than another reboot.
From the messages on the screen it is possible to find out what went wrong and why. If you can boot into safe mode after a crash, tools are available to investigate the crash information and perform further diagnostics. Microsoft offers its own tools, but there are other options, such as NirSoft's BlueScreenView freeware, which takes care of all the complex analysis and puts the BSODs recorded by the system into a compact report.
Consider a hardware replacement if there is no BSOD. If automatic restart is disabled when a system error occurs and the computer simply restarts without crashing, you may be dealing with something more serious. One potential cause is faulty memory. Run the Memtest86+ tool overnight on the computer in question to make sure everything is in order.
Try an in-place repair or a complete reinstallation. An in-place repair – installing Windows on top of an existing Windows – doesn't touch the applications and user settings, but it does cause the system components to re-initialize. You should only use this option if all else fails.