Instructions
Turn the PS3 on. From the XMB bar (the menu that loads when you turn on the PS3), scroll to "Settings." Select "Network Settings." Select "Media Server Connection." Select "Enable." The PS3 will begin to search for a media server connection.
Open Windows Media Player. Click the arrow on the "Library" button. Click "More Options."
Click "Library." Click the "Configure Sharing" button. Place a check next to "Share My Media." You will see an "Unknown Device" that is actually the PS3. Click "Allow" and "OK."
Access the Windows Media Player streaming video on the PS3 by selecting the "Video" section on the XMB bar. All the video files in the Windows Media Player library will be listed. Select the video you want to watch.