My computer does not detect pen drives and other USB devices like iPod or external hard drive

If none of your USB devices detect ,this could be due to wrong registry entries. i.e you need to delete UpperFilters and the LowerFilters registry values.

1. Open Start >> Run, and type "regedit" (without double quotes), and click OK.
2. Locate UpperFilters registry value. it resides in the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E980-E325-11CE-BFC1-08002BE10318}
3. Click on Edit menu, and select Delete and click OK.
Note: If you receive an error when you try to delete the registry subkey, you may not have correct permissions to edit the subkey.
4. Locate LowerFilters registry value. It resides in the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E967-E325-11CE-BFC1-08002BE10318}
5. Click on Edit menu, and select Delete and click OK.
6. Exit Registry Editor and restart your system.