Oracle 7.3, Windows 2000

I have inherited a system from another contracting company. Oracle 7.3.4 is on a Unix server. We are using Windows 2000 on the client. The instructions from the former company say to install Developer 2000 for Windows 95 (on a 95 machine). The 95 disk has been installed on the Windows 2000 and now I have to recompile code written in Forms 5.0. When I try to recompile, I get error message FRM-10043 saying that a .FMB file is not an Oracle Form. Does anyone have any clues? Could the problem be caused by not using Oracle 8.1.6 (Developer 6) on the client?

Thanks.