How to remove write protection on my sandisk cruzer flash drive usb?

When the required keys in your Registry don't exist, you can create them manually, then enter the required value manually in the right-hand pane.

The outcome will be just the same as if the keys were already there.

There's a short tutorial on that here: http://www.computerhope.com/issues/ch001349.htm

You could disable the write protection as below:
1. Plunge this drive or memory card to a computer. (Of course, you should use a card Reader to connect your memory card.)
2. Click “Start” on the taskbar to open “Run” and type in “regedit”.
3. Hit “HKEY_LOCAL_MACHINE” to expand “System”.
4. Find “Current Control Set” in “System” list to click “Control”.
5. Check whether there is a key named “Storage Device Policies” to change the digit in the “DWORD value” box into "0" and press “OK”.
But, if you cannot find the key named “Storage Device Policies”, you are supposed to create a one: right click “Control” to create a new key and name it as “Storage Device Policies”=> right click this new key to open “DWORD Value” and name it as “write protect”=> Double click it to change number.

My only question is: after I do all this then what? I followed all these steps and had to create the key manually, however, the value was already set to a "0". So is that it from there? That is supposed remove the write protection? 'Cause it didn't work for me!   This is getting very frustrating!!  

Perhaps, this could help you:
http://www.irongeek.com/i.php?page=security/thumbscrew-...