It should say on the box, but USB 2 is a lot faster than USB 1. You'll find that if it's an external hard drive it should be USB 2 anyway. You'll need USB 2 ports in the back of your computer though for it to operate at full speed. They look exactly the same as normal USB ports, but are faster. To check if your ports are USB 2, go to Control Panel, System, Hardware then Device Manager. Click on + sign next to Universal Serial Bus controllers which is at the bottom. In the list that comes up if there is one that says "USB Enhanced Controller" then you have USB 2, if it doesn't say enhanced then you have USB 1 and the drive will work at the slower USB 1 speed. You can also buy internal PCI cards with USB 2 sockets on them.