Are you running your Flex Application and continually getting the error below?
"Flex Builder cannot locate the required version of the Flash Player. You might need to install Flash Player 9 or reinstall Flex Builder.
Do you want to try to run your application with the current version?"
Description:
This error is not a critical error and if you click on the Yes button the application will most likely run the way the you expect it. The reason this happened may have been because you recently did an express install or just an upgrade to your Flash Player.
Solution:
To get rid of this window constantly popping up you need to do one of the following:
1.Reinstall the Flash Player
Follow this link and reinstall the Flash Player. Get the latest Flash Player Debug Version
This may or may not solve the issue.
2.Put the missing file in the folder that Flex is expecting.
As you can tell Flex is looking for the dll in the folder C:/Program Files/Mozilla Firefox/plugins but if you look in that folder I would wager that the file NPSWF32.dll is not there. Where you will find the file is in the following folder C:/Windows/System32/Macromed/Flash . Simply do a copy and paste from the Macromed/Flash folder into the Firefox/plugins folder and you will eliminate the error.
3.Point Flex to another browser.
If the above method doesn't work (which it should) then you can use IE as your default browser. The way you change your default browser in Flex is by going to the menu and clicking Window >> Preferences. 
This will pop-up the Flex preferences window. From within the Flex preferences window select General >> Web Browser and then change the Browser from Firefox to IE as shown in the image below.
4.Last resort reinstall Flex.
Below are two links to help you trouble shoot.
Get the latest Flash Player Debug Version
Find out what version you have.
As always Happy Flashing
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