but some are not - check what the manufacturer says about compatibility.
If it is compatible it will be VERY SLOW. You could get yourself an addon PCI USB 2.0 card that would be easy to install and MUCH FASTER for reads and writes from Newegg.com or many other sources. If the computer is a laptop (you don't mention) it would be upgradable to USB 2.0 with purchase of a USB 2.0 PC Card.
I have a computer with usb 1.1.....I am interested in purchasing a external hard drive that is usb 2.0...if connected to my 1.1 usb port will the 2.0 device work?