Do as Merlin has suggested and remove the device in the device manager. Depending on your version of your operating system (I'm assuming you're on windows) the drivers may be automatically installed on reboot, or you may have to use the CD that came with your computer/firewire card, or download them. If you have troubles, post back with Operating Sysytem & version, and the type of firewire device (eg Belkin Model XXX Firewire card, or onboard firewire on GA-7N400 Pro2 motherboard).
And Merlin, I wouldn't expect firewire to dissapear any time soon. USB2 is a fair competitor to Firewire400 (the initial IEEE1394 standard) but Firewire800 is, well, twice as fast. I'd expect it to continue to be used on professional level devices, but would expect the dominance of USB to continue on lower level devices where speed is not so important, but price is (firewire is more expensive to implement as well as being less popular). You'll also note that more and more computers are coming with Firewire standard (for example, Gigabyte now make many motherboards with firewire built in), particularly towards the enthusiast end of the market.
