After install, USB devices ID'ed but can't be accessed

Installed Windows 7 64 bit operating system yesterday. This was an upgrade from Vista. The computer will recognize anything that is connected to the USB ports, but it is unable to access the device. For instance, it shows my Seagate external hard drive but I cannot access it. It is all the same for any external device, although USB mouse is functional. New drive letters DO NOT show up under Computer. It also recognizes my Dell printer, but again it cannot access it.

Now here is something very serious... after I take the external hard drive off of this computer and put it on another, the other computer will not recognize it. I have 4 external hard drives, all of them were working just before the Windows 7 upgrade. Now none will. Another thing, the system will not even access flash drives. I have tried many. Again, it shows they're there, but cannot access them nor give them a drive letter.

I need to be very clear on this... even if I put a brand new, right out of the box, drive on this computer, it will not find the device. Is it possible that an operating system upgrade can damage a USB device?

Performed all diagnostic tests supplied by Dell, Microsoft, and Seagate. On my Seagate drive, there was an error for "generic short test" and "generic long test". On my printer, "no driver present", although all new drivers are loaded.

Have you installed the latest BIOS for your desktop? 1.0.13 was released to support Windows 7.

Have you installed any of the Dell drivers for your desktop?

Did you do an in-place upgrade? If so, you should consider doing a clean install instead. Quite often an upgrade just doesn't work like it should.

If you have space left on your drive, create another partition for your data and then copy the important files to the new partition.