Open the Windows task manager and end task on any Opera processes that are still running.
Ten, in Windows Explorer, in both "C:\Users\yourusername\AppData\Roaming" and "C:\Users\yourusername\AppData\Local", right-click on the "Opera Software" folder, goto "Properties" and click the "Read only" box so that it's clear (all white) and click "Apply". Then, switch to the "Security" tab, make sure your username is in the list and make sure it has full permissions (all set to "Allow" except special permissions). Then, apply and okay out.
If that doesn't do the trick, rename those "Opera Software" folders to "Opera Software old" and then try to start Opera.