Firewire is probably better...it;s much faster although there might be some complications running windows off of it. Here's the steps to set up the external for all of this.
1. Assemble External
2. Hook up to Mac.
3. If it works, partition into 2 partitions; one bing NTFS for Windows and the other being HFS+ for your videos.
4. Install all firmware updates.
5. Download and run the latest BootCamp Assistant.
6. Follow all of the Bootcamp Assistant's instructions.
7. When you are supposed to insert your windows instillation cd...instead of choosing the harddrive on your mac to install to...choose the partition on your external.
8. Bob's your uncle!
I'VE ALWAYS WNATED TO SAY THAT!!!!