Hi Calmar
DONT GIVE UP!!!!
I suggest that you download PAF5, if you're not sure you've got it on your computer, then INSTEAD OF CLICKING ON YOUR FILE, look for a PAF5.exe file and open that. Then go to File/Open on the menu bar and go and look for your tree file from there.
It's just that, when it's first installed, the links to any files already on your machine haven't been set up. By starting with the PAF program and then opening your file from inside it, you should be back where you were.
Ignore all references to Adobe - you only need that for looking at wordy help stuff, not the program or your tree!
Fingers crossed.
Angela