Remove the write protection using diskpart commands in the command prompt window -- open it with a right click run as administrator. Here are the commands in the order that you need to use them:
select volume n (where n = the problem volume)
attributes disk clear readonly
attributes volume clear readonly
After each of the last two you should get a response that it was successful if it was.
Here is a page that lists all the diskpart command syntax: http://technet.microsoft.com/en-us/library/cc770877%28v=ws.10%29.aspx