This problem had users all the time and posted here.
If you actually browsed a few page back on this topic you'd find your solution
All you need to do is to change DesktopTD15k_swf.ext to...

ok so i did it right and when i download the swf it downloads as (DesktopTD15k_swf.ext) but i found how to get it in text document then changed the stuff then when i go to change back all it wants to...