Can't change a guest account

I'm running Vista SP 1. I have an account called 'owner' that was created at
some point early on when I got the machine. It is my primary user account.
I have recently found out that the account is a 'guest' account and not a
'standard' or 'administrator' account like I thought. Therefore, I can't run
certain programs or even Windows Update under this account. Can anyone tell
me how to change this account to an 'administrator' account? I've tried
everything I can think of and need some additional help.

Thanks,
Lane