Ctrl+R then type regedit /*comment: opens registry editor*/
then Navigate to the following key:
Computer\HKEY_LOCAL_MACHINE\SYSTEM\
CurrentControlSet\Control\StorageDevicePolicies
Double-click on the WriteProtect value in the right-hand pane of Regedit.exe. Change the Value data from 1 to 0 and click OK to save the change. Close Regedit and restart your computer. Connect your USB drive again, and you should find it is no longer write protected.
source: pcadvisor