I need a usb external hard drive for my ps3. I need it for backing up my ps3. What is a good one that has 120gb?

Bonus Question: Will it work for transferring files from an old hard drive in your ps3 to a new one on the same ps3?

External hard drives aren't worth it. Don't waste your money on one. Your not able to get the data out or select it to play it once its in there. If you want to back up your PS3, you can do it 3 ways.

1. Go into Settings > System Settings > and from there you can do a whole back up that the system will do itself. But it takes a long time (like 3 days to be exact), so its not worth it.

2. Get yourself a little USB flash drive and copy the game saves you have onto there from the Saved Data Utility (PS3). If a game save ever corrupts in your system, you just plug the flash drive into the PS3, open the files with triangle and display all, and from there copy the game save back onto your PS3.

3. Make a new user and just copy your game saves onto that user. You go into the Saved Data Utility (PS3) and copy your game saves onto the user.

Note that for 2 and 3 that you will have to delete the game saves and re copy them once in a while as you progress more in a game.

I do that all the time and it works great and takes no more than a minute to do each time. So its worth it.

Hope that helps.