I have succeeded in installing Adobe Reader and Skype.
Unzipping on the PC is the first step. Then, as in a treasure hunt, see if there's a text file to give you the next one. This may be to copy the files into a My Documents folder to facilitate transfer to the PDA by ActiveSync.
With Skype there was no instruction, but running the biggest .cab file on the PDA did the trick. Soon the Skype screen and a test call option appeared, wow, VoIP worked!
The downloaded Navigon 6.2 software still resists all efforts, and Navigon's TS are sending duplicate replies by email in slow time.