I'm glad you solved the issue! And thanks for posting back such a detailed solution.
lighttpd and ngnix are "lightweight" HTTP servers (I would recomend Cherokee, but its Windows builds have been broken for quite some time), and XCache is a PHP op-code cache (like Wincache). The point here is maybe these things will work better for you and as a side-effect, as they are multiplatform, you won't be tied to Windows.
How is breaking your PostgreSQL+Moodle test install? I mean what errors are you getting. My experience on administering Moodle is mainly on Linux, but AFAIK it should be as easy as installing and configuring PostgreSQL (getting an optimal config may take some time if you are not used to is plethora of parameters, but for testing the out of the box config is ok), checking the pgsql PHP module is installed and works, and performing the usual Moodle install. As you're doing a test installation you could try the latest RC of 9.1, which has some small improvements for Windows (like the pg_ctl one).