Main account is guest account by mistake

[Lane]

Somehow my primary account name Owner got switched to a guest account. This
means that I can't run certain software, can't get to Windows Update and do a
host of other things. I have tried in vain to switch my account to
administrator or even to a standard user but can't. The account says
Administrator but really it's a guest account. To do anything I have to
switch to another account that I created as Administrator. Does anyone have
ANY suggestions for what I can do short of contacting Microsoft? I'm running
Vista Home Premium, just downloaded SP 1. I have the UAC turned off.

 

[Smithsonian]

Im not really sure this will work but you can try.
Open a cmd
make sure you type this exactly

net user <new username> * /add

if you dont want to set a password just press enter
I belive the account will be created as an administrator