You might like to try this link. It leads to a beta .msi install of a free (as in it costs nothing) alpha-win32-native port of PostgreSQL.

It wasn't totally trivial to locate on the pgsql website, but a careful step through the FAQ following the win32 links, led straight to it.

The port is alpha and "not for production purposes", but as you want it for learning, it should be good enough until the port gets more stable.