Goto the My computer Icon on the desktop or My Computer Link in START, right click on it, click on Manage.
On the left side of the Window that pops up, click on Disk Management.
Disks must be initiated before you can format them, perhaps yours need to be corrected, and you can do that here.
Also, perhaps they are just required a Drive Letter Change. You can do that here also. (right click on the external hdd an click change drive letter path)
Any HDD, internal or external, thats connected to the computer, will show up here, even if it doesnt show up in the My Computer Window. As long as it is powered.
You do not need a Disk for External HDD's. Ones that come with one just put supportive software like backup related things, but most just have that information on the HDD itself.
How do you have them hooked up the computer? Directly into a usb port on the computer? or through a USB Hub? Do all of your USB ports work? Is the HUB, if thats what your using, powered only from the USB connection or from a wall outlet?
Have you tried it the HDD's on any other computer/Operating system?
Edited by s1lents0ul, 13 August 2010 - 08:23 AM.