So I loved Freespace 2, and the first one came up on sale for like 3 bucks so I bought it. But it won't start... kind of. I can hear the intro sequence, and the opening menu music, but there's no way for me to view the game's screen. It just shows me my own desktop at a reduced resolution.

It was 3 dollars, so I'm not clamoring for a refund or anything, but is there a way to fix this? I was pretty excited about seeing what led up to Freespace 2.

https://fsnebula.org/knossos/

You can play beither "retail" (that is: the game as it came out back then but with improved compatibility with modern hardware and OS and more resolution options) or with enhancements (the "mediaVPS" be warned though it will be along download), you'll need either Freespace 2 installed or the GOG backup installer on your hard drive (Knossos will extract the files from it during the installation).

I have the same problem, but Knossos says it needs the retail version. What do you know about that?

It needs either the retail version (the original CD rom release), and already installed copy of vanilla Freespace 2 (steam, GOG or original disc release) or the GOG installer on your hard drive, I used the latter (mostly because I wanted to have a clean install and using the CDs directly is a pain in the ass).
Probably there is something that doesn't allow Knossos to detect the files on your hard drive.
I suggest you ask in the Hard Light Productions forum, the developers of Knossos write there and should be able to help you.

OK. Thanks.