Step 1: Download latest version of MapSource from Garmin. Step 2: Rename file extension to a .rar instead of .exe Step 3: Use WinRar to extract to a folder (instead of running exe). Step 4: Run MSmain.msi file, not Setup.exe. Step 5: Be happy. Note that "setup.exe" runs the check to see if you already have MapSource installed, then it executes the MSmain.msi file to install the application. By executing MSmain.msi file directly, you skip that step and just get a clean installation.