Your problem has noting to do with double system.
I guess you must make Windows XP as the default system, when there's problem with XP, or if the systems destroy something released by memory, the system will automatically restart.
When you shut down your computer, the system need the release memory, when the system memory release failed or some problem happened during the release, the Windows XP will take this as a problem, and then it will automatically restart. After restarting, the system is clean, and there’s nothing to prevent the system to shut down, so you can close your computer successfully this time.
My way to solve the problem: click "My computer"---》property---》advanced---》Startup and
Recovery---》Setting, remove the hook from the "Automatic Restart" option.
If you need to completely solve the problem, you need to fix your system with problem, such as
Almostly, this problem will not happen to windows 7 system.
Anvisoft--A leading Internet security solutions provider