It's a little dodgy converting to either one but it can be done. Are you sure your DVD Player can't play NTSC and PAL? Most players can. Check your manual just to be sure?
I was reading some tutorials about converting NTSC to PAL and visa versa yesterday actually. I'll find them for you and edit this post.
Site:
http://forum.digital-digest.com/showthread.php?t=56599
You can also edit the head in the DVD (after it has been copied onto your computer) with IFOedit. But you can't be sure it will work on all DVD Players.
Both ways are a bit dodgy. And you can't guarantee either way will give you a working DVD. You're better off buying a DVD Player which can play both PAL and NTSC. Most players can be bought cheap now days