When progamming an AIR application, you may want to make use of the applicationStorageDirectory available via the flash.filesystem package to store temporary files/folders. You can find where your system is storing these files by doing something like the following:
trace(f.nativePath + ' is where my file is stored');
var f:File = File.applicationStorageDirectory.resolvePath("Test.txt");
This will give you an absolute path to the local system file storage location. Handy for multi platform applications, as Pc and MAC based systems will use different default storage directories.