What does this mean?

[PaulWog]

I have connected my receiver to my computer via HDMI. The signal is lossless audio (coming from an ATI 5770 graphics card supporting all the dolby formats, and full lossless audio).

What I'm confused about is my receiver doesn't have anything light up like it says it should in the manual. It says if it's receiving different signals, it will read "dolby _____" on it (fill in the blank to whatever it's receiving).

Instead, when I set it up for the proper signal, it reads "PCM" for a couple seconds.

The surround works perfectly (I've tested it and it definitely 100% works), however I'm confused as to why my receiver reads "PCM".

Additionally, how would I get my receiver to play 2-channel music (basically everything in my library) with some surround? When I had it hooked up via an optical chord before (it wasn't lossless), I could select all the different kinds of modes. Now that my receiver is connected via lossless HDMI, I can't select those modes anymore.

Receiver model: Pioneer VSX-520-K

Thanks.