Recently, my trusty Windows XP (despite the end of Windows XP support) did some updating of software and failed to reboot (when it reaches the Windows startup screen, it will reboot itself) after that. Not even using using SAFE mode helped. But using SAFE mode with command prompt, I notice that it stops loading the driver files relating to AVG.
So using the repair option to get me to the command prompt, I use the DEL command to remove all the AVG driver files (note you have to remove one by one as the wildcard does not work in this case) in the C:\Windows\System32\drivers directory and voila Windows was able to reboot again!!!!
Updated 17May2014: my windows XP is behaving arratically again, and the fault has been narrowed to AVG, uninstall and install the free alternative antivirus AVAST instead, will observe to see if it is more stable. Goodbye AVG!!!
Note *: AVG is the freeware Anti-virus program.