Flash MX 2004.
fl.fileExists(fileURI)
fileURI A string, expressed as a file:/// URI, that contains the path to the file.
A Boolean value: true if the file exists on disk; false otherwise.
Method; checks whether a file already exists on disk.
The following example displays true or false in the Output panel for each specified file, depending on whether the file exists.
alert(fl.fileExists("file:///C|/example.fla"));
alert(fl.fileExists("file:///C|/example.jsfl"));
alert(fl.fileExists(""));