I didn't download the application from Google Play and got the apk from a website and installed it on my tablet. But the app wasn't the one I needed and it was just making offers for me to get other apps.

Now I want to uninstall it but in "Manage Applications " all the buttons there are locked and can't be pressed, including the uninstall and move to SD card.

What do I do to get rid of it? It's taking up space on my internal memory.