In reply to Gavin Taylor:
I think that's just a USB2 hub and Firewire hub in one box - it doesn't convert one to the other. I've never seen a Firewire to USB2 converter and would be surprised if they existed.
Kenny - unfortunately I don't think there's any option for upgrading an iMac to USB2, however yours will definitely have Firewire unless it's one of the very oldest ones with a CRT screen and tray-loading CD drive. If you want to connect an external hard disk, CD/DVD drive, iPod, video digitiser or high-end sound gear, Firewire is the way to go. For everything else, there's Masterc... er, slow old USB1.1.
Dominion and assorted snidey commentators: in the time Kenny, Mick and I have spent NOT having to piss about with the insides of our Windows/Linux PC's, we have more than earned any extra cost associated with the Mac - or alternatively gone out and had a variety of worhtwhile life-enhancing experiences not involving staring at a computer screen ;-P