I have exactly the same system installed on both my notebook and desktop computer -- Windows 7 Home Premium x64 Edition with Service Pack 1 and Polish Language Pack. On one of them (notebook) I can access external USB 80 GB 2,5 inch hard drive without any problems. On the other one (desktop) I can't access it at all.
The only difference is, that both systems were installed:
- using different installation DVDs and
- using different Activation Keys.
Of course, there is a slight difference in hardware, but not that significant:
- my desktop runs on Intel i3 540 / 3 GHz with 4 GB of RAM,
- my notebook has Pentium Dual-Core T4200 / 2 GHz with also 4 GB or RAM.
There were numerous of situation, that I wasn't able to access some disks on some computers, but usually it was a slight problematic case, like Windows claiming that disk is not formatted, while it actually was. And restaring computer or changing USB port usually helped. But for the first time I met situation, where an USB device is fully accessible, when plugged to one computer and Windows does absolutely noting (acts like no new device would be plugged in) on second machine.
Basic (in this situation) operations like restarting computer or unplugging and re-plugging device again brings no effect. Windows remains "deaf" for this device. Also, changing USB ports brings no effect. I tried four of them.
The only thing I noticed was, that when I plugged it into my keyboard (which is also 2-port USB hub) hanged both keyboard and mouse attached to second USB and Windows notified my, that it failed installing driver for an unknown device. Unknown device? WTF! I've used the same keyboard (USB hub) with my notebook and there was no problems with accessing that damn disk!
Since device is completely not detected, I can't use any software to fix this problem and simply have to resign from whatever I wanted to do with this disk. Now, that's a pretty IT fuckup!