I would suggest that they just add '.' to their existing path, probably using a semicolon as a separator since they're running Windoze.

ie:
Code:
include_path='.;c:\php\'
If they won't do that, tread carefully as you move forward and try to run advanced scripts such as Zen Cart. There may be other stumbling blocks in their server configuration that might create headaches.

If they won't make the change, there may be a way to force it using programming ... but IMO that's a last-resort situation, and as I said, there may also be other problems later.