play iDVD project on Windows computer

How long is your movie? YOu could simply export is as a QuickTime file, burn a data disc and then the PC only needs to have QT in order to play it (free download from Apple).

Unlike your Mac, PC's have tons of different software DVD players. A lot of the software is "free" crippled versions of one's where the vendor wants you to buy the "complete" version. If a DVD isn't playing in a PC, it is USUALLY (not always) one of two issues:

1) The PC doesn't have a DVD player. Don't laugh. It happens. Often.
2) The DVD software isn't there, or isn't up to date.

Mike

In addition to what Mike said, you might try burning your project onto a different brand of DVD (Verbatim, Fuji, HP) and at a lower speed, around 4x. It might be that your PC player is having trouble reading the particular disk you are using. Also check your Quicktime PC settings.