FireWire is touted as a cross-platform standard, which is great -- unless you don't have a FireWire port on your computer. FireWire is often used in audio/visual equipment, but most computers don't have a FireWire port. USB is a more common technology, and your computer almost certainly has at least one USB port. Since FireWire and USB ports are shaped differently, they aren't compatible. If your computer doesn't have a FireWire port, you have a few options to get the data from your FireWire device.
Beware of FireWire-to-USB Adapters
The obvious way to convert a FireWire connector to a USB connector is to use an adapter. A plethora of inexpensive adapters abound, but they aren't a good solution. According to Videomaker.com, FireWire-to-USB adapters do not work because the FireWire and USB standards use different languages. Adapters simply change the plug type; they do not translate the languages. You are better off finding a more permanent solution.
External Hard Drive
If you need to transfer large files, using an external hard drive with FireWire and USB ports is a good option. Connect a FireWire device to a hard drive using the FireWire port, then connect your computer to the hard drive using the USB port. You can purchase a complete hard drive, available from NewerTech and LaCie, or you could purchase a hard drive enclosure, such as the OWC Mercury On-the-Go. If you purchase only a hard drive enclosure, you need to provide your own hard drive.
Another option is to connect your FireWire device to a hub, and then connect the hub to your computer. IOGear and Belkin offer hubs that have FireWire and USB ports. These hubs enable you to directly access files on the FireWire device.
You can add a FireWire port to your computer using an ExpressCard, which works for Macs and PCs. The Sonnet FireWire/USB ExpressCard includes two FireWire ports and one USB port. Simply insert the ExpressCard into your ExpressCard slot in your computer to add a FireWire port. Alternatively, install Sonnet's Tango PCIe to add three FireWire ports and three USB ports. Another option is to simply add a PCIe card with only a FireWire port. These are available from manufacturers such as StarTech.com, HP and Rosewill.