Data Editor Help

Not sure where to post this, but have tried researching on the Internet and couldn't find a solution. Downloaded the Editor from Steam but when I go to play it, first I get the error 'Unable to find dsetup.dll' and then, afterthat, another 'XML prasing error: not well-formed (invalid token) at line 1 of '. Found thread somewhere that suggested removing the Settings folder, so tried that but still nothing! I'll be very annoyed if it's Steam, or if I have to take the game back!