It's a little late, but this is a follow up to an old RTA thread.

First, if anyone is still looking for a good RTA program, I came across a completely free RTA program that works great. It's called Praxis, by Liberty Instruments. You can download it and the related documentation from the Liberty Instruments Website.

It is actually intended to be used with their audio measurement hardware, but the software still lets you use some features even without their hardware, including RTA measurements. And it's truly free with no expiration period or anything like that. I have been using it for a couple of months with no problems.

While I was updating my webpage, I decided to do a quick write up about using a PC as an RTA with Praxis that some may find useful.