Instructions
Go to Settings and scroll down to select "Network Settings."
Scroll all the way down to Media Server Connection. Click this to allow the PlayStation 3 access to media servers on your home network.
Start your media server on your computer of choice. Check your programs documentation to ensure that you're sharing the files correctly; some programs require you to choose shared files manually, while others allow full access to all the files on the computer while they're running.
Go to Photo, Music or Video, and select your media server from the options. If your media server is running but not listed, choose the "Search for Media Servers" option. If your media server still isn't listed, reboot the PS3 and then the server.
Navigate to a file on your server, and click the "x" button on your controller to start the media. It may take a few moments for the server to start, depending on the speed of your connection, how you're connected to the Internet and the size of file you're playing.