Yes, open the file in a text editor. If it was created in P4 it'll have { Version { number 4.0 (or 01 depending on service pack) at the top Pro Pack will have 4.2 and I should image version 5 will have number 5.0 (plus service pack) at the top. This applies to cm2, pp2, cr2, pz2 and all the other active files.