>>I don't think there is any specific version of VFP information stored in the .FXP. There is in the .EXE, but not the .FXP.
>
>There has to be something because if I try and run a VFP 8 fxp in VFP 5, with out the source so it compile on the fly, I get "Object file "myprog.fxp" was compiled in a previous version of FoxPro (Error 1195)"
>I'm sure I would have to open the file with low level handle and read a specific byte but was hoping someone already had found out.

You might get different behavior based on what the fxp needs to do. There is also file-associations at the OS level....