Windows 7 user account suddenly changed to a guest account

Question

I'm the only user and my account has (had) administrator privileges. After a routine reboot, I logged into my account as usual, and soon found that I could not install software. I didn't have permission to write to the Program Files folder. I couldn't write to any folder outside of my home folder. I checked User Accounts in the Control Panel, and my account was now listed as a guest account. I have the built-n Guest account off, incidentally. I'm unable to change my account type back to administrator or create a new account because guests can't do much at all, really. Does anyone have any idea how to enable the built-in Administrator account from here or from a rescue disk? I should be able to fix my account easily from the Administrator account, no?

The changes I had made since last reboot that may have been responsible for the unintended demotion of my account are: I uninstalled the .NET framework 1.1. I deleted the ASP.NET user account that .NET 1.1 creates and leaves behind.

Solution

Boot into your System using Advanced Startup Options and select Command Prompt with Networking

By Default there is an Administrator account Hidden and without password and accessed over safe mode. If you aren't able to login through that, reset its password using following steps.

After logging in Open Command Prompt with Admin privileges (if it doesn't work, try opening it normally).

Type net user and press Enter Then you'll see the list of accounts.

There must be an account named Administrator/Admin

If yes, Type: net user Admin * or net user Administrator * (based on your user account available) and press Enter

Type in the new password for Admin/Administrator Account.

Now reboot and boot your system in safe mode and login with Administrator.

After successful login, Goto User Accounts Management, and change your account type from guest to Administrator.

Reboot normally and login to your account.

Comments

[Scorpion99]

Try a System Restore for the last previous checkpoint

[blazingshambles]

All fixed up, thank you. Now I would really like to know what caused this. A serious bug in .NET 1.1 is all I can come up with.