Cannot uninstall old OS installed application and upgrade to a new version on Android

What is the easiest way to upgrade an application that was installed on the OS? I cannot delete this application from Setting->Application List - "Uninstall" option is unselectable.

BTW: I have changed a few things on androidmanifest.xml, like added more activities, changed the st开发者_开发问答art up(launch/main) activity. The package is the same. I have updated version name and code.

When I try to download a new version of the application, the OS installs TWO applications with the same name. Of course I want the previous to be replaced by the new one.

Have you tried uninstalling it through adb?

You'll need to connect your device to your computer via the USB cable and try this:

adb uninstall your.package

This is all assuming that you have the Android SDK installed and updated with the tools (adb).

And here is some more info on adb:

http://developer.android.com/guide/developing/tools/adb.html

You can delete the app in Command Prompt (Windows) or Terminal (OSX/Linux) with the command: adb uninstall com.packagename.package from your phone/simulator. Be sure to have 1 phone or 1 simulator open at the moment you execute this code.

Here is some more info about the ADB: http://developer.android.com/guide/developing/tools/adb.html