How to Install Apps from Unknown Sources on Android mobiles:
This is the way you can allow installations of apps from non-market applications. But, what exactly ‘Unknown sources’ refer to? Unknown sources refer to the apps that you download from websites and the apps that you sent via email etc. You can again tap the ‘Unknown sources’ option to disable it at any time. For AT & T phones, this option is unavailable and they need to rely on various sources in order to install apps from unknown sources. Installing Android SDK, using command prompts or using Sideload Wonder Machine (SMW) will help AT & T phones to install the apps from unknown sources.