Today, I tried it and it worked for some reason! But still getting an memory error message when quitting FSX, but only when PMDG 737 has beed previously loaded in the sim, but I can live with that. :-)
I am having the same problem. Win-XP and "run as admistrator" doesn't help. Just purchsed this aircraft hoping for the best. Trying to get repaints of United and SW from the main site to install. "Oops! This variant is not installed" doesnt help very much. So, I am hoping there is a solution.
Thanks again.
PS I can't delete existing paints either!