It was replaced by Write to Text File. You can still access the old VI, though. It's in "LabVIEW 8.x\vi.lib\Utility\file.llb."
I can see how it might be difficult to get the filename that was selected if you leave Write to Text file unwired so the user is prompted. The easiest way around that is to put a File Dialog before you write to the file so that you can see what file was selected.