I've developed a simple Android project on Eclipse. Then I export the application as unsigned application onto my PC. Then I copied the application on to the SD card. Then I tried to install the apk file by clicking on it. I also made ensure that I can install applications from sources other than from market. But my application while installing says that application not installed. I've tried one solutions in stack overflow which suggests to install AppInstaller and try from there. Even though it's not working. 

What can be the problem with the installation?

Any ideas ?