* "Who Wants to Be a Millionaire?" airs at 8:30 on WJLA.
* The 100th episode of "3rd Rock From the Sun" on WRC.
* And the season finale of "The Real World" on MTV.
An interview with Sen. John McCain (R-Ariz.) about his run for the presidency (MTV, 3:30 p.m.).
NHL Hockey. Tampa Bay at Washington (HTS at 7).
Stopwatch (CC) documents the life of Frederick Winslow Taylor, who introduced "scientific management" to the workplace (Channel 26 at 2 p.m.).
Intimate Strangers: Unseen Life on Earth (CC). Part 1 of a four-part series exploring the wonderful world of microbes; tonight, a look at the ancient DNA of microbes as the root of our family tree (Channel 26 at 8).
The Real World wraps up its Hawaii stint. Issues yet to be resolved include Colin and Amaya's romance and Ruthie's battle with the bottle (MTV at 10).
Movies in Time looks at the accuracy of the new Joan of Arc film, "The Messenger" (History Channel at 11).
60 Minutes II (CC). An interview with Microsoft Chairman Bill Gates, made before Friday's court ruling that his company wields monopoly power (Channel 9 at 9).
Dateline NBC (CC) reports on mysterious circumstances surrounding the death of a prominent Cincinnati surgeon (Channel 4 at 10).
Spin City (CC). Mike targets a rich political donor (Amy Irving) to give to the mayor's campaign (Channel 7 at 8).
Buffy the Vampire Slayer (CC) consoles Willow, who is down because Oz is powerfully attracted to a female werewolf (Channel 50 at 8).
3rd Rock From the Sun (CC) marks its 100th episode with the Solomons spending a murder mystery weekend with Mary (Channel 4, 8:30).
Who Wants to Be a Millionaire (CC). Night 3 of a 15-night run (Channel 7, 8:30).
Dharma & Greg (CC). Kenny Loggins serenades Abby and Larry, while Tommy Chong (Cheech and Chong) gives Greg some career advice (Channel 7 at 9).
CAPTION: "3rd Rock From the Sun," with French Stewart, John Lithgow, Joseph Gordon-Levitt and Kristen Johnson, marks its 100th episode tonight at 8:30.