[GENERAL] Ruuning two instances of Postgres on the same machine

[Robert James]

I'm currently running Postgres 8.2 on Windows XP.  I would like to use some
8.4 features, but I don't want to migrate my 8.2.  Is there any way to run
both instances together? Are there any problems with that?
Alternatively, is the procedure to move from 8.2 to 8.4 without data or
function loss documented anywhere?
Thanks