This problem has resurfaced again, where my external drives were not recognizewd by my PC. The given advice was a great help, but what is the procedure if "Lowerfilters" is not even present in the Registry reference as shown above? There was an "Upperfilters" there ok.
If you set the DEVMGR_SHOW_NONPRESENT_DEVICES environment variable, Device Manager will show you the "ghosts" of past devices that are no longer connected to your system (or in the case of USB devices, were perhaps attached to a different USB jack) if you enable Show Hidden Devices. From there, you can right-click and uninstall all these non-present devices. (Don't worry, the OS will detect and reinstall the drivers automatically when devices are reconnected.)
I check non-present devices regularly, and I'm always amazed at the amount of crap left in the registry. In addition to having every three devices (USB Mass Storage Device, Disk Drive, and Storage Volume), for every flash drive ever plugged into the machine, I seem to have practically every permutation of USB device and USB jack imaginable. Even upgrading firmware seems to leave a ghost of past devices in the registry.
1. Click Start, point to All Programs, point to Accessories, and then click Command Prompt. 2. At a command prompt, type the following command , and then press ENTER: set devmgr_show_nonpresent_devices=1 3. Type the following command a command prompt, and then press ENTER: start devmgmt.msc 4. Troubleshoot the devices and drivers in Device Manager.
NOTE: Click Show hidden devices on the View menu in Device Managers before you can see devices that are not connected to the computer. 5. When you finish troubleshooting, close Device Manager. 6. Type exit at the command prompt.
Note that when you close the command prompt window, Window clears the devmgr_show_nonpresent_devices=1 variable that you set in step 2 and prevents ghosted devices from being displayed when you click Show hidden devices.