here's a tip i found the hard way for my ps3.
IF you are doing this for videos, don't even bother with media center, it sucks in every possible way.
ps3mediaserver.blogspot. com
Best software ever. Transcodes and plays almost any video file i've used to date, with exception of x-files i had an issue with. Plays mkv's etc.
I believe it can do pictures and music too but i don't use it for that and probably won't anytime soon. You could try it out.
Also if you want to stream HD content you will need to put your PC and PS3 on wires. The wireless NIC in the ps3 is not able to handle much more than 25mb/s ish. With 720-1080p you will want at minimum 50-60 (wired usually runs 70-80 for me...).
Anymore questions let me know but yes... don't even use windows media, so difficult to do anything with.