O, got the 300ER showing now, I double checked I had the installer released after 8 August 14, I uninstaled ALL PMDG, I also manually deleded the folders from simobjects/airplanes, then Manually delete the PMDG 777-200LR, PMDG 777F, PMDG 777-300ER, and PMDG 777-GMC folders in C:\Users\(Your Windows Username)\AppData\Roaming\Microsoft\FSX\SimObjects. Manually delete the PMDG_777X_3.ini file in the FSX/GAUGES folder.
then ran reg cleaner,
Then ran the 200 installer, inout licence, then the 300 and it shows and is working.
I however have still the issue of
Failed to load texture:
$WINGLIGHT
$FLAPSTCLLIGHT
$CABINLIGHT
$MLGHB
Ronan