There are a few different ways you can reset the password.
If you created a Windows password recovery cd, you can use it to reset the password.
If you have another admin account on the machine, you can use it to reset the password for your wife account, as well as, backup the data.
If the machine has Windows 8 or newer and the account that you can't login to is a Microsoft account (not a local one), you can reset the password on the web through Microsoft's site.
If you have a Windows installation CD, you can load into the cd, pull up the command prompt (Shift F10) and replace the utilman.exe file.
There's a number of password reset tools such as Microsoft DaRT tools that you could use to reset the password.
Lastly, if all else fails, you can take the hard drive out, connect it to a different machine as a secondary drive and backup the data, then reset the drive through the recovery or reinstall Windows.