Mac ai file/WinPCSign issues?

A friend recently bought a vinyl cutter and is using WinPCSign on a trial version on his Windows XP laptop.

I brought him a file to test, an Illustrator CS3 file, saved as an .ai, from my G4, on a 4gb stick.

Neither WinPCSign nor Corel Draw X4 he was using would open the ai file... we kept getting an error about it being a compressed file.

Is this like the old Mac to PC, PC doesn't recognize the Mac code, issue? Could it be something related to his WinPCSign being a trial version?

Anyone have a workaround? Do I need to save or export it as something else?

I'll maybe have to try them all... eps, pdf and maybe export a cdr and see if his Corel likes that...

he's not a graphics guy, he just bought the thing so he doesn't have to deal with a sign company/vinyl cutter, because he wasn't getting any service... I just need to help him figure out what he needs to tell people who want him to do stickers from existing files...

thank for the input

yes, it was an issue that it did not like the CS3 file... illustrator 8 and eps worked fine