Running the setup program overwrites all files in the folder where you initially installed the software (default: C:\4tops\accessmailmerge).
In the likely case that you already activated the product with the Mail Merge Installer to one or more of your databases you will have to find where the copies of the Tools folder and accessmailmerge??.mde library file are located. You will then replace them with the Tools folder and accessmailmerge??.mde library file in the installation folder.
This copying of the files can be done in two ways: