Bundling PostgreSQL

Hi,

I'm the author of an email server for Windows which can use PostgreSQL as
backend. My software also supports MySQL and Microsoft SQL Server. Since a
lot of people find it hard to manually install a database server, I'm
thinking of bundling PostgreSQL with the software. Not only they find it
hard, they find it a bit annoying that they have to install a database
server when what they really want is to install an email server.

The main problem I have is that my software installation currently is
roughly 4MB. If I added all the files included in the PostgreSQL
installation, it would become at least 10 times as big.

Does anyone know if there's a "slimmed-down" version of PostgreSQL which
only includes the file needed for "basic" functionality to work?

Kind regards,
Marti nKnafve