open job file
If the version of the job file is 6 or 7 you can open it with powerpcb versions 2.01, 3.51, 4.0, or 4.01. I am not sure about 5 as I do not use it.
If it is version 3 or 4 you have to open it with dos version 6 or 7, then save it as 6 or 7 then open it with one of these windows versions.
Converting from 3 or 4 might have some problems with copper polygons, I am not sure as I do not open version 3 or 4 files very often.
If you want me to convert the file for you pm it to me as I have most of these versions installed including v6 of perform for dos.