Unable to start or reinstall manger

i 've been using manager without any problem over a year.suddenly i find it does not run.and tried to reinstall but still not succesful.what am i to do. facing a big problem as i lost all my clents detail.

Do you get any error message?

once it says “manager is already running and cannot be restarted”
when tried to reinstall it says newer version is installed in the computer"
when i tried to install it fresh from the internet it installs the manager but doesn’t run.;

OK, so you tried to install the latest version from the Internet. It installed, then you say Manager doesn’t run. When you say it doesn’t run, do you get any error after installing the latest version?