Try the following.
First thing to do is to close down everything belonging to ESM using Task Manager. Then check Services (Control Panel --> Administrative Tools) and stop service(s) related to ESM.
For problems with Windows installer use Windows Installer Clean Up utility
. This tool cleans up all Windows installer related traces from your computer. It will allow you to run an (un)installer where it was getting blocked because it couldn't find a needed file or says the products is already installed. This tool does not uninstall a program.
Look in Windows Installer Clean Up utility for ESM and when there remove it.
Now the installer of the old program will no longer see remains of the previous version. When no left overs of the previous installer around you should be able to install the new version. Let us know how things go and if problems arise what they are.