Well, export the project to iDVD, and burn it with iDVD. This should make a generally playable DVD, and it will adjust the quality settings accordingly so that it fits onto the DVD.
Once done, take a look at it.
You can also click the Quicktime option in share, and then choose the Divx format (.avi) and adjust the settings. As long as the windows machine has the divx/xvid/avi codecs on it, should work okay.
I think you can also export as mpeg and multiple other exensions that should move over to windows without too much hassle, but if you are going to use DVD I'd try the export to iDVD route. Should be plenty of tutorials on how to do it out there. But I imagine that since it's OS X, it's basically point and click.
Interested to know how it goes,