There will be something missing from tomorrow's opening of Erol's Video Club's newest Washington outlet: Beta cassettes. Like all Erol's stores opened in the last year, the Good Hope Road location will stock only cassettes in the VHS format. While most of Erol's older, suburban stores still carry both formats, the opening of this one means that the majority of the chain's stores within the District offer only VHS, and the chain plans to continue the VHS-only policy at all future locations.

The Beta format is falling out of favor nationwide. According to the electronic industries association, 16 percent of the nation's VCR homes use Beta equipment, but fewer than 10 percent of the VCRs being sold today play Beta cassettes. Even the Washington area, which has an unusually high concentration of Beta machines, is drifting more toward VHS. One area retailer estimates that a quarter of the area's VCR owners use Beta -- down from a third a year ago -- and many of them have both Beta and VHS.

This shift has not gone unnoticed by movie studios and other cassette suppliers, who are getting choosier about which titles they issue on Beta tapes. Beta owners don't have to worry about finding the latest hit movies on tape -- not yet, at least -- but two major video suppliers have recently formalized plans to reduce the number of Beta titles they offer. RCA/Columbia has announced that it will limit Beta rental releases to the movies it judges most popular; HBO Video has adopted a similar policy and will also eliminate Beta cassettes from its sales promotions unless it already has Beta inventory on hand. As a result, HBO will not produce any new Beta copies of its latest batch of $19.95 movies -- including "F/X," "The Mean Season" and "Sweet Dreams" -- and current HBO rental hits like "Hannah and Her Sisters" and the forthcoming "Platoon" probably won't be around in Beta when their prices eventually come down.

Closer to home, Erol's plans to continue offering Beta tapes in its VHS/Beta locations "as long as the products remain available," and has no plans to remove Beta inventory from stores already carrying the format, according to a company spokesman.

Burnett's Best

Carol Burnett has come up with an antidote to the new TV season: repeats. Burnett has assembled "My Personal Best," a pair of home video compilations from "The Carol Burnett Show." Each of the one-hour, $29.95 tapes offers a handful of classic sketches and production numbers from the series selected by Burnett herself. In Volume 1, Carol dons a pair of window drapes -- curtain rod and all -- as Starlet O'Hara in "Went With the Wind," and elicits the longest recorded laugh in the show's 11-year history. In an earlier "Family" sketch as Eunice, her "Gong Show" rendition of "Feelings" gets cut off in midmoan. Volume 2 presents Bernadette Peters, Anthony Newley and the series cast in an extended Shirley Temple takeoff called "Litte Miss Show Biz," as well as a turn by Sammy Davis Jr. as an entertainer who grew up with Burnett in the South. The tapes are due next month, about the time the new season starts looking old indeed.

Spock Speaks

"Star Trek IV: The Voyage Home" hits video stores next week, but Trekkies who can't wait that long may want to look into a new variation on the paperback novelization scene just out from Simon & Schuster Audio. The publisher has adapted the "Star Trek IV" novelization for audio and put it out on a 90-minute audio cassette priced at $8.95. The abridgment, read by George Takei (Mr. Sulu), features additional narration by Leonard Nimoy (Mr. Spock). The latest "Star Trek" novel, "Strangers From the Sky," is also available in the same format.

The Love Goddess Remembered

When Frank Sinatra was offered top billing in the 1957 Columbia film "Pal Joey," the story goes, he insisted that the honor go to his costar, Rita Hayworth, saying that "Rita Hayworth is Columbia." Now, in honor of the star, who died this year of Alzheimer's disease, RCA/Columbia Pictures Home Video has donated $25,000 to the Alzheimer's Disease and Related Disorders Association and has repriced its entire Hayworth collection at $29.95. Four new Hayworth films will also come out at that price next month: "Pal Joey" (which also features Kim Novak and a number of Rodgers and Hart standards that weren't in the stage production), "Salome," "Tonight and Every Night" and "The Loves of Carmen." Previously released films affected by the price cut include "You Were Never Lovelier" and "You'll Never Get Rich" (both with Fred Astaire), "The Lady From Shanghai" (costarring and directed by Orson Welles, whom she was divorcing at the time it was filmed), "Gilda," "Miss Sadie Thompson," "They Came to Cordura," "Fire Down Below" and "Angels Over Broadway.