Vista - Can't create new user account

OK, so the issue you're having is that the main profile got corrupted, the secondary works OK, but now that you are using he secondary, you have create a third (tertiary) profile and cannot kill (remove) the main (original) profile, right?

That is correct.

I'm having the same issue, but I can't create a new user using "netplwiz" or

"Hit Start -> Run (Windows + R) -> cmd

From here type:
net user USERNAME /add"

I only have the one user and it is the admin account, I don't know what to do from here.

I am having the same problem. When i try to create an account using "net user evan /add" it returns "The Command Completed Successfully" but the directory C:\Users\evan is not created and there is no entry added to the registry at HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\ProfileList.
The new account does appear on the logon screen but when I try to log on it returns the error message "The User Profile Service failed the logon. User Profile cannot be loaded."
Thanks for the help so far. sfc found and fixed a few courrupted system files.

hey, never mind, I figured it out. The directory C:\Users\Default was missing important files (NTuser.dat, ntuser.dat.log1, etc.).