Skip the mini-cd, just go to the Digitrrax site and download the latest version, and put it in a folder on you hard drive. When prompted for drivers just go to that folder instead of the min-cd in you drive. Problem of large hard drives - so much space you never clean anything up - mine are still there even though once you get the driver installed, you don;t need that folder any more.
Compatibility mode is simply a Windows XP virtual machine. That’s a good chunk of the price difference - paying for that license of XP to run. I installed it just to see how it worked, have not found ANY reason to actually use it so far and I’ve been using Windows 7 exclusively since it was released.
Altough the OP has a NEC DCC system; the Digitrax PR3 can be utilized as a stand alone Doecoder Programer with Decoder Pro and a short test track next to the computer. You don’t even need a Digitrax system to use a PR3.
I work away from home and use the time on the road to add DCC decoders to my locomotives. I have a Digitrax DCC System, but use Decoder Pro and a PR3 with my laptop. My home layout uses Decoder Pro, but I have an old Digitrax MS100 and my old Windows XP desk top PC to run the layout and program decoders. I have a Power Pax for sound decoders. A Power Pax is not necessary with a PR3.
I would suggest that he simply put the PH PRo next to the PC and run the BUSS and CAB wire to the layout. There won’t be any wire length limitations that way. It will also make it easy to put a program track at the PC.