USB is theoretically faster than firewire, but it is shared with other resources in the computer. The more things connected to your USB ports, the slower your throughput will be, so disconnect all external USB hard drives, disconnect your external mouse and external keyboard to give yourself the best chance at getting a clean encode without dropping a frame. Firewire is a dedicated path into your processor.
As for whether the Movie Box will work with your system, you will need to check the specifications of your exact computer and processor against the system requirements for MovieBox http://www.pinnaclesys.com/PublicSite/us/Products/Consumer+Products/Home+Video/Studio+Family/Studio+MovieBox+Plus+version+12.htm
In looking at the specifications for the Toshiba laptop you have, it uses an extremely old processor (introduced in April 2008) and a slow hard drive. These two things may result in dropped frames which will put your audio and video out of sync. According to Pinnacle’s website and the computer specifications that I found on a CNET review, your computer is below the minimum specifications to edit SD video, and if you plan to edit HD video, I would almost guarantee dropped frames.
I hate to be the bearer of bad news, but I think you will need to get a more powerful computer, preferably one with firewire included. A desktop will give you the best price to performance ratio and will give you the ability to upgrade as you advance and your needs and desires change.
