Be careful about Google results on this subject.
The 1st results contain virus/paid D1Fea~12.cab software (https ://www. solvusoft.com - don't touch it! It's trialware and worse - malware)
the questions on proper websites (microsoft/flightsim/simouthouse for example) have zero or unsuccessful replies.
Have you tried a proper uninstall - do a complete system clean to remove any left over garbage, then temporarily close your anti virus program - then reinstall properly from the CD's.
It seems many people seem to have W10 issues with FSX - though they are still the minority.
Do you have a separate partition (D Drive for instance)? If so try the new install on there.
Also I would seriously consider moving to P3D ($59.95 for Academic). It's where MSFS would be today had microsoft not dropped it. I would never go back TBH.
Simplicity is the ultimate sophistication. – Leonardo da Vinci