Just click on the "log out" button and it'll remove the saving bit.
Alternatively, if you're using Windows 2000 or XP the actual cookie will be in ...
C:\Documents and Settings\{your username on pc login}\Cookies and will be called
{PC Username}@volkstorque.co so go into
C:\documents and Settings, do a search for
*volkstorque* and delete the file.
Option 1's the easiest and the password in the cookie can't be decrypted anyway