Upgrade 7.2 to 7.3

A while ago, I played around a bit with PostgreSQL 7.2 and created a
test database (think it was called mydb).

Since then I've upgraded Linux and it also upgraded PostgreSQL to 7.3.
Now I'm ready to start doing some proper stuff but I can't start the
postmaster. It says I need to upgrade my database, but I don't care
about the old database.

Is there any way I can remove the old database and start working with 7.3?

Thanks,
James