I havent tried Media Share yet, but I use eStrongs File Explorer and Linda File Manager on my Droid to transfer files over Wifi. eStrongs is easier to setup, but they both work fine.
I will play around with Media Share tonight and see if I can figure out how it works.
Is your PC setup to allow file transfers on a network? I think its called File and Printer Sharing. I had another PC on a home network so mine was already setup. Its possible that could be the problem.