What error messages are you getting on the PC? What kind of PC do you have?

I'm curious as I have the eTrex Legend. like yours (but the B&W version). I haven't bought any of the $100 dollar CD's (yet) so I don't know how they install. Windows XP should detect the serial cable and the Garmin eTrex GPS unit. Are you trying to take a topo map FROM the eTrex and copy it onto the PC?