I can not use my computer to modify or delete any data from any external USB disk. If I plug in the same disk into another computer, there is no problem. This started right after I did an update of Dell Precision Optimizer, and may involve BitLocker or a problem with the USB hub. I noticed the system disk (c:) was encrypted and whenever I plugged in a new drive, I got the BitLocker dialog asking me to encrypt or not. I have decrypted c: and disabled the BitLocker service, but the problem persists. For any external drive, There is no "delete", "cut", or "rename" option in the windows explorer context menu, and using the "del" command says "The media is write protected." Diskpart says no disk is read-only. Setting HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\StorageDevicePolicies\WriteProtect = 0 has no effect, as does "attributes disk clear readonly" in diskpart.