downgrading to 7.3.2 from 7.4.1 under Cygwin

Hi Folks,
I've refreshed my Cygwin distribution and haven't noticed that postgres is
also being upgradeing. So it has been upgraded to version 7.4.1. Starting
"pg_ctl start -D /usr/local/psql/data -m fast 2>&1 &" sends an error
message like this:

$ FATAL: database files are incompatible with server
DETAIL: The data directory was initialized by PostgreSQL version 7.3, which
is not compatible with this version 7.4.

I'd like to downgrade to 7.3.2 because all my customer run that versin and I
have to test my software on that version. Should anybody suggest me ho to do
that?
I've already rerun Cygwin installer, but since it was running many times the
previous config opiton doesn't "remember" my earliest version of postgres. I
can't force it to downgrade. :o(

It would be very useful to try out 7.4.1 but not on my "production test
system". Can I set it up separately on the same cygwin machine? I plan
running them separately, but if it is possible to run on separate ports at
the same time, than I choose that.

Many thanks for helping me

-- Együd Csaba