Installation of ADE

ADE has stopped working on my laptop. Despite repeated reinstallations and reauthorizations following Adobe Help instructions, it will not reinstall successfully. After reinstalling, when I download from Overdrive I receive a message to install ADE and when I click Yes to the question," do you want the following program to make changes on your computer ...Program name Adobe Digital Editions 4.5.1", I get a message from Adobe Digital Editions 4.5.1 Setup that"  Adobe Digital Editions 4.5 is already running. Please close ADE and try again". It keeps relooping through this sequence.