Is it possible to manually edit the driver to make it function on windows XP?
I guess there are many differences, but it must be possible for simple drivers, kind of porting the locations / buses they use?
Do you mean without re-compilation? If so its not recommended.
If you are willing to compile then use appropriate WDK and select appropriate build environment and try to build. You may have to change the code depending upon any APIs changed/availability.
Also note that drivers are compiled per OS i.e. there are different build environments for WinXP, Windows 2003, Windows Vista, Windows 7 etc.