It works on my computer (XP), but when put on my brother's computer (with vista) it does not get assigned a letter. I've read every posting about this I can find on google, even tried a couple of programs designed to assign letters to USB devices and neither worked. It shows up in device manager fine, but when I go to disk manager it doesn't allow me to change the letter. It doesn't give me the option at all. It's partitioned into two partitions and when I click on them it gives me the option but it's grayed out so I can't click it. Grrr! The computer has 2 internal HDD, 3 DVD drives, and 4 removable HD in it. I changed the 3 DVD drives to X, Y, and Z, one of the internal HDD from D to W, and the 4 removable ones to P, Q, R, and S. Then I reinstalled the external HDD. Still nothing. There are no network drives at all. And I assume it's the admin login because it's the only user set up. Anyone have ANY ideas???