If you have a Windows Phone 7 then make sure to register it now so that you can find it later if you need to. Visit https://login.live.com/. Enter your Windows Live ID and password to sign in. Go to the “find my phone” option and enter the settings area. Make sure that you have selected the box that reads “save my location periodically for better mapping.” This will allow you to locate the phone on a map as needed.
If you lose your Windows Phone 7, go back into this area of the website. From here, you can choose to ring your phone (if you think it’s near you) or locate it on a map. Having enabled the mapping tool, your handset should show up on the map. You can see if you left it at a previous location or if it has been stolen. If stolen, you can disable and lock your phone from the website to prevent the thief from using it.