NNewcomb,

First you must uninstall FS from the old computer, and then install it on your new one. During registration process, when entering key product, MS knows when you are trying to install FS on more than one PC. Don't forget to backup [Logbook.BIN] file (Start > Documents > Flight Sinulator X Files > Logbook.BIN) to avoid losing your flight hours and awards earned. After installing, paste saved [Logbook.BIN] file on new [Flight Simulator X Files].

Pinatubo.