You can create a shortcut that forces windows to shutdown, I have Windows 98, I am not sure what applies for XP,
right-click on desktop;
select 'new' then 'shortcut';
in the command line type
C:\WINDOWS\RUNDLL32 SHELL32.DLL,SHExitWindowsEx 4
name the shortcut 'shutdown'.
Download Force Shut-Down Software
I am sure you have searched on Google because I just did and it brings up a lot of relevent results and I am sure there is a solution to your problem;