I found another way to install the map with out mapinstall.
you need to have usb drivers and webupdater installed on pc then go to command prompt and type this
C:\GARMIN\WebUpdater\WebUpdater.exe /upload_file rgn=49 path=C:\Garmin\GMAPPROM.img -autorun usb /i
both paths need to match your own pc program/file locations.
it delete old map and installs new one. now mind you the c340 would not take a 1.55gb map file so i found a 1.4gb version and works great.