Am I doing something wrong? Help with DLNA

I bought a Samsung LN52B750 & didn't know anything about the DLNA until I started playing around with the tv. I've set up my server to allow the tv to see files on my pc. i have no problems accessing the files:jpeg, mp3, mpg, wmv. But anytime I try to play or view any file it always says "Not Supported File Format". I've tried over 50 different mp3's & wma files and also 20 something video files and none of them work. What am i doing wrong? Can anybody help me?