Replaces the extension of a file name with a new extension
_WinAPI_PathRenameExtension ( $sFilePath, $sExt )
|$sFilePath||The path in which to replace the extension.|
|$sExt||The string that contains a "." character followed by the new extension.|
|Success:||The path with new extension.|
If the file name does not contain an extension, the extension will be attached to the end of the string.
Search PathRenameExtension in MSDN Library.