Go to the following Key in your register:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control
right click on Control and choose New and then Key.
Name it StorageDevicePolicies
right click on StorageDevicePolicies and choose New and then DWord
Name it WriteProtect
double click WriteProtect and change the Base to Decimal
Exit Registry, restart your computer and then again re-connect
your USB pen drive on your computer.