HOLLYWOOD, Oct. 17, 2000 -- Whether the Olympics or network television, it's a cutthroat world out there. This from ABC's "Who Wants to Be a Millionaire" files: NBC and CBS are reportedly asking their network stars to not appear on special celebrity episodes of the Regis Philbin phenom, Daily Variety reports. But viewers will be treated to 10 former U.S. Olympic athletes. Last spring, funnyman Ray Romano from CBS' "Everybody Loves Raymond," "X-Files" G-man David Duchovny of Fox, and Vivica A. Fox from the CBS series "City of Angels" appeared on "Millionaire" alongside such notables as Lance Bass of 'N Sync and Queen Latifah to high ratings. Variety reports that Martin Sheen of NBC's "The West Wing" and Conan O'Brien tentatively agreed to appear this time around but backed out after NBC officials suggested otherwise. The scheduled TV celebrities so far are