Hywok

I got the "bad serial number" error when starting up, so following the guides i found on here, I tried to delete the registry keys inside the folder. Problem is, i can't seem to delete the Arma 2 OA folder. I could delete the Arma 2 folder fine, just not this one folder. The error I get is "Cannot delete Arma 2 OA: Error while deleting key". I've checked all my permissions and they are all allowed to my account, and I can edit other keys just fine. It's just this one key. Same for editing also, I can't go inside it and change any of the values. Help? Thanks in advance.