One of the greatest things about Windows 7 is that it can remember your Usernames and Passwords to a variety of different systems. For example, if you log on to a network at work, a network a home, etc. If you have access to another clients' SharePoint site as a trusted partner, Windows 7 can remember that Username and Password. It also works for Shared Network Drives on different networks, etc. All you have to do is type in the path or URL, and — bang — you're in.
This works with systems that accept Windows credentials, Certificate-based credentials, or generic credentials.
But sometimes, you might wonder which systems you're able to connect to automatically. If you want to know, just go to Start and Run; then type: control keymgr.dll and it will show you all the connections where you're hooked in to log-in automatically with the wonderous Windows 7.