Will not open? So how do i get to run?

Since you don't explain what won't open, I'll guess at one of two things.
The splash just sits and the Sim won't start, delete the log file and it'll start.

I'm having what seems to be the same problem. FSX has been running great since release, then suddenly this past weekend it just stopped responding. Only thing I can think of is I downloaded Microsift IE 9 Beta (I work in web development so this is a common practice).
I start up FSX and it sits at the splash screen. All night if I let it. I've repaired and uninstalled/reinstalled twice, on separate drives even. Still no good.
I searched my files. Where is this log file you mention?
Any other ideas?
Thanks in advance.

I'm guessing you have W7.
W7 C:\Users\%username%\Documents\Flight Simulator X Files

If you are uninstalling use this guide, it works.
http://support.microsoft.com/kb/888846

Yes it works on W7.

Actually I'm probably the only person who uses 64 bit Vista and loves it! Never had a crash or any problems. Works great on my desktop and my laptop. I could go months without a reboot. My Mac requires rebooting more often than my Vista PC. Go figure.

And as far as the removal, DUH! The registry. I failed to clear out the registry. I"m sure that's my problem, I will attempt that this evening. I can't wait to get flying again.

For grins and giggles, I'm going to install 2004, 2002 Pro and 2000 if it works. 2Tb of disk space, why not?!

The registry is something no one bothers with and that usually the main sticking point.
Clean that and your problems should be cured.

When you mentioned deleting the log file, I was looking for a systems log. Not the actual logbook. So I made a backup of the logbook and deleted it from the folder and everything works great...

except...

Now I've lost hundreds of log hours, my completed missions and all of my achievements. And let me tell you, landing that cub on that bus was no easy feat!

If I send my corrupt log file to Microsoft, I wonder if they can save it.

I need a signature. hmmm.

Sorry but now you have something to do...start over.

I'v also lost God knows how many logbook entry's from corrupt files. but look at it this way: Now you have another reason to play on the computer!

Right here in our own download section, a logbook recovery tool!!!

https://flyawaysimulation.com/downloads/files/1675/fsx-logbook-recovery/

It worked! I have my logbook and achievements back!!

Now if I can recover my completed missions I'll be back to (somewhat) normal!!

I forgot that existed, glad it worked.