Dual Boot Win 7 & XP - XP has stopped loading

2 years ago I created a Win 7/XP dual boot set up using this excellent tutorial: http://www.sevenforums.com/tutorials/8057-dual-boot-installation-windows-7-xp.html It has run faultlessly until now when the default Win 7 still loads perfectly well, but when selecting XP it now boots until the blue Windows XP background screen appears then hangs. This is the screen that would have "Windows is...