I thought I would use the same technique as with the Galaxy Tab S - load the app on a SD card, into the phone, press the desired app and, "Cannot open file".

OK. I'll trick you. Copy the app to Download in Internal Storage, press the app and, you guessed it, "Cannot open file".

Suggestions please.

1. Note I have no desire to open a Google Account.

2. I am using XP on a lappy.