Not so fast!
Flight Simulator cannot run because its SIDE-BY-SIDE configuration is incorrect.
Check application event log or run sxstrace.exe

Looked at event log, which just told me to do sxstrace.exe .

Windows help told me that I could avoid this problem by doing a regedit.
I found the required "HKEY_LOCAL_MACHINE" ok, but there was no such thing as" _COMPONENTS\"

Tried to reinstall Acceleration, hoping it would align stuff, but it refused to run.
Pumpkin! I said.

I reinstalled FSX, which took a long time.
Right, now I'll upgrade to Acceleration.
Not until you have activated FSX you old fool!
OK, I'll activate it.
No you won't, because I'm not running FSX, on account of your Direct X isn't version 9....reinstall it from the FSX disk.
Windows ran that during FSX install, I saw it; but obviously it decided that because I had a later Direct X, I wouldn't want to overwrite it.
Search found several Direct X entries in the computer, but I had no idea how to step back to V9; there's no prog. to uninstall
I am stuck, any ideas please?