Windows update cause Adim lockout

My wife computer did an automatic Windows update, and turned off and turned back on. Now she is locked out of her admin account the password is invalid. I login into the guest account, but I can not do/ get to her work..no programs or data. I know she should have not use admin account. It is a Windows 7 on dell P-4 2.4Ghz with 2 GB of ram How do I get back in?