You can copy files across the network with it. As dbmzk1 said, you can set up a web server to do this. However, by far, the easier way is to use something like Windows Media Player 11 sharing. This allows your PS3 to see all the same music, videos, photos that are on your PC library through a media center like interface, which can be used to view the content on PS3 AND also copy the files across. Very easy to do and plenty of guides/info on this forum and on the internet. (And much quicker than using a portable hard drive). Also portable hard drives are locked to the FAT32 system to be seen by PS3. If you wish to copy files larger than that that FAT32 supports then you need to use the media sharing method.
rp2000