Have you experience a system that hangs up just after Windows XP logo appears on the monitor screen but works fine when set to safe mode? Try the solution presented here,it may fix the problem.
Try to start the unit at safe mode,go to system properties and remove the graphics card device and re-start the system, XP will try to re-install the driver of the graphics card and will continue on your desktop and Windows is now back to normal.
In cases where you can't enter safe mode,try re-installing Windows, if still does not work refer to my previous post "Windows XP Perform Endless Reboot"
This solution will be applicable also on system that graphics resolution is hard or cannot be set on higher colors.