Connecting a HDD to the AirPort Extreme Base Station (AEBS) by itself will not make it a media server. Instead, you will need either a hardware or software DLNA-compliant media server to do this.
As an example, I have the following setup:
- 2 TB WD HDD attached to a 4th Gen Time Capsule. On this HDD I have my media library ... both audio and video.
- A 2011 Mac mini running OS X Lion and Twonky Media Server software.
- A "slim" Xbox 360
- A Hardon Kardon audio receiver w/Bose speakers.
In this configuration, I have a software media server (Twonky) that can access the media files on the WD HDD and stream them to the Xbox 360. In turn the Xbox connects to the audio receiver. You can just as easily substitute the PS3 for the Xbox and a PC for the Mac and basically do the same thing.