So you're using Windows 7 Ultimate, along with the preconfigured virtual Windows XP machine. One day, after installing some applications, you're suddenly presented with a login screen: you need to supply the password for the XPMUser account.

You don't remember ever specifying a password. Your Windows 7 password doesn't work. You try a blank password, you try combinations of your usual password, you try the trivial ones like "password" or "12345", but none do the trick. You reboot the VM, and now you cannot get into it at all; whereas previously, the VM desktop came up, now you're blocked by, you guessed it, a password prompt. Online fora are of not much help either; they tell you that you probably set up a password (you know you didn't), they tell you to try "password" or "12345", they tell you to reinstall the VM tools inside the virtual machine, or reinstall the whole VM (losing all your installed XP applications and settings, of course.)

The one thing they don't tell you is the actual solution. (OK, there may be Web sites that do tell you that. I just haven't found them.)

Replace XPMUser with your actual Windows 7 username. Enter your Windows 7 password. Be happy.