Run 2 versions of Postgresql on one machine?

hi,

I just took over a project done by somebody else of some C extension of
Postgresql 7.1.3. And now I have to port it to pl/pgsql. The guy who
developed it said he didn't get it running under 7.2 for some reason. And I
suspect it might not run properly under 7.4.1. Since I only have one machine
so I really hope that I could run 7.1.3 and 7.4.1 on the same machine and
run his code on 7.1.3 while developing pl/pgsql on 7.4.1. Now can anyone
give a hand on whether this can be done, and if so, can you give me a little
direction on how to do this?


Many thanks,

Wei