silent install of postgres for an embedded purposes

Hi. I am new to postgres and I am porting an application to windows that is
using postgresql as it's backend. I am also trying to do a silent install
of postgres. I would also like to install postgres on a usb thumbdrive. It
is just for demo purposes.

1) Can you have more than one instance of postgres on a machine? I have
tried the following and it is failing because I have postgres installed.

msiexec postgresql-8.2int.msi /qr INTERNALLAUNCH=1 ADDLOCAL=server,psql
SERVICEDOMAIN="%COMPUTERNAME%" SERVICEPASSWORD="postgres"
SUPERPASSWORD="postgres" BASEDIR="c:\postgres"

2) Can you install it on a usb thumbdrive? e.g.

msiexec postgresql-8.2-int.msi /qr INTERNALLAUNCH=1 ADDLOCAL=server,psql
SERVICEDOMAIN="%COMPUTERNAME%" SERVICEPASSWORD="postgres"
SUPERPASSWORD="postgres" BASEDIR="f:\postgres"

3) How do I import and export a database? I assume I have to do some type of
backup and recovery.