Version 5 compile error

I'm having trouble compiling some Turbo Pascal source code which was
written using version 6.  I'm trying to recompile it using version 5 and I
get the error message "Error 72: Unit file format error" in relation to a
.TPU file.

Is there any hope of compiling this code with version 5. If not how do I
get a copy of version TP 6. I don't really want to have to go to version
7.

Any ideas, please email to osbor...@hort.cri.nz

Thanks in advance.