My Star Wars - The Clone Wars Blu-Ray comes with a Digital Copy. How exactly do I convert the WMV to MP4 to play on my son's Sony PSP? Without having to buy something of course?

The WMV file is probably copy-protected so that you can't convert it.

Has anyone here successfully converted a Digital Copy to MP4 format for playing on a Sony PSP?

I did some searching, and it seems the digital copy on "Clone Wars" also includes a version for iPods. This would be in MP4 format, although I don't know if copy protection would allow it to work on the PSP or not. And if you've already used the code for the WMV version, you might not be able to download the movie again in the other format.

There's also this: http://www.pspvideo9.com