You need to install the postgres and/or ruby-postgres gems. I'm not
sure if both are needed as I've had it installed for a while now and
can't remember. Beyond that, I believe the adapter name in the
database.yml file should be postgresql not just postgres.
It looks like you're missing some development libraries, but I'm not
sure which one(s). I've never tried to get rails working on a
Windows box, so I really can't be of much more help. On *nix, I'd
probably make sure I have ruby-dev installed for the version of ruby
I'm using. You could look around and see if there is a ruby
development installation for Windows.