in os x you by default burn iso 9660 (or somethiung close to that i think) cds, which are the standard windows format for a burnt cd. pc readily read these cds without a hitch, as does your mac. i have never tried to burn a new session on a pc burnt disc, but i see no reason as to why this would not work. your best bet is to just give it a try. who cartes if you kill a $.25 cd? just make sure you still have that info on your hard drive.
edited the iso number...