External USB hard disk drives not recognized after uninstalling Acronis True Image

Symptoms:

• External USB drives / USB sticks are not recognized.
• In the Windows event log a message similar to the following one appears:
  "The driver \Driver\tdrpman273 failed to load for the device"

Applies to:

• Acronis True Image Home 2011/2012

Solution (found in the Acronis forums):

1. Entirely remove Acronis True Image.
   (if you have trouble uninstalling it from the Control Panel, use the Cleanup utility provided by Acronis. Caution: This removes all Acronis products from your machine)
   
2. From Acronis KB 14871:

(!) After using Cleanup Utility, it is strongly recommended not to reboot the machine, go to Start -> Run -> regedit, and verify that there are no snapman*, tdrpman*, timounter strings in the following keys:

• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E967-E325-11CE-BFC1-08002BE10318} -> UpperFilters and LowerFilters
• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{71A27CDD-812A-11D0-BEC7-08002BE2092F} -> UpperFilters and LowerFilters

Good luck!