Make Sure XP is installed first and linux (Lilo actually) will do the rest.
When you boot it should come up with the options...
Linux (Or what ever distro you have)
Windows (Or Similar)
Failsafe
and... something else that i've forgoten coz i never use it
Hope this helps too.
But DON'T edit the windows files.... Windows is the work of satan and will kill your PC/Linux box
Peace
David