ECADES ago, a Mad magazine cartoonist, Dave Berg, offered a vision of how the Soviet Union might win the cold war. Here in America, a never-ending succession of labor-saving devices - escalators, cars, remote controls and so on - had already created the most sedentary society on earth. All the Soviets had to do was wait until we evolved into living Weebles, complete with tippy, round bases and vestigial leg sprouts. Then they would just knock us over with the butts of their rifles.

The cold war is over, but the trend toward the elimination of all muscular effort continues apace. If you're a movie lover, for example, you can now rent a Hollywood film by downloading it directly to your Windows PC, saving yourself two exhausting trips to Blockbuster. You don't even have to return the movie when you're done; the movie file automatically deletes itself from your hard drive 24 hours after you first click Play. Of course, you're also spared the caloric expenditure involved in rewinding a tape.

Since the demise of movies.com and intertainment.com, only two contenders are left standing in the downloadable-movie racket:

movielink.com and cinemanow.com. (A third, starzondemand.com, is in the works.) Each charges about $4 or $5 to watch a recent movie, roughly the same amount the video store does.

Now, if you wonder why anyone would ever want to download and watch a movie on a PC, you are not alone. The downsides are daunting.

First, each movie file is huge; you need to clear a landing strip of 500 to 800 megabytes on your hard drive. Second, dial-up users need not apply, and even with a cable modem or a digital subscriber line, all of that data takes a long time to arrive: 20 to 90 minutes for a typical two-hour movie depending on the speed of your broadband connection. (You could probably bike or walk to Blockbuster in that time, but of course that would entail exercise.)

Worst of all, you have to watch the movie on the PC, which usually means listening to the soundtrack through cheap speakers, watching on a smallish screen and sitting on a chair that was never intended for leaning back, motionless, for 120 minutes. CinemaNow's site offers instructions on connecting your PC to your television, but the layout of your home, and your tolerance of ugly wires, may rule out that configuration.

Still, plenty of people are willing to overlook these drawbacks. About 30 percent of American households are equipped with high-speed Internet connections, and thousands of people regularly download movies from software-piracy sites like KaZaA.

You can probably guess where all this is going: Movielink and CinemaNow were created as legitimate, Hollywood-sanctioned alternatives to free, unauthorized services. (Movielink was started by Sony Pictures, and joined by Warner Brothers, Paramount, MGM and Universal; CinemaNow is financed by Microsoft, Blockbuster and Lions Gate Entertainment.) Their emergence roughly parallels the creation of the much-hyped pop-music download services that the record companies created, following precisely the same "if you can't beat 'em, join 'em" philosophy.

There's a key difference between the movie-download sites and the music-download sites, however: the music sites show a glimmer of promise.

How CinemaNow stays in business is a marvel. The site is so marred by typos and poor programming, it could have been a high school sophomore's first Web design project. After you provide your credit-card information during the registration process, you're asked for it again on the next screen, and yet again each time you buy a movie. It's like a hovering Blockbuster employee who follows you around the store, asking every 30 seconds: "And you're sure you can pay for this, right?"

CinemaNow is a subscription service. You pay $10 a month for unlimited access to about 400 of what CinemaNow calls premium movies. Sounds good - until you realize that all 400 run along the lines of "Oliver Twisted," "Addicted to Murder III: Bloodlust" and "Witchcraft XI: Sisters in Blood." (Wish I could claim credit for such wit, but those are actual titles.) Clearly, CinemaNow is stretching the word "premium" from here to Ripley's Believe It or Not.

Another 300 movies are in the 18-and-over category called After Dark. (Come to think of it, maybe how CinemaNow stays in business isn't such a mystery after all.)

Where does CinemaNow get this cheese? The site's invitation to "filmakers" (sic) to submit their homemade creations on VHS cassette may be a clue. ("Please remember to include your name," it says.)

Most of these "premium" movies are available only as streams, meaning that they play directly from the Internet without being downloaded to your hard drive first. On one hand, you don't have to wait a long time for downloading; movies begin playing after only about one minute. On the other hand, the video quality is therefore dependent on the speed of your connection, which generally means that you can't watch the movie at full-screen size.

Note, too, that streaming movies take another minute to respond each time you try to jump around using the scroll bar, making you wonder if CinemaNow shouldn't be better named CinemaMomentarily.

CinemaNow also offers about 110 more recognizable productions: "Swimfan," "One Hour Photo," "National Lampoon's Vacation" and so on. The only major movie companies represented are MGM, Warner Brothers, 20th Century Fox and Lions Gate. ( Disney, Sony, Paramount, Universal, DreamWorks and Miramax are missing.) Even if you've been dutifully paying your $10 a month, these movies cost you an additional $4 or $5 each.

Most are genuine downloads, easy to navigate on playback, and high in quality. Of course, quality is a relative term; movies from Movielink and CinemaNow offer about the quality you will find on VHS tape (although the text in credits is especially blurry), and the sound is in stereo, not surround sound.

Even here, CinemaNow is a disappointment. The selection of movies is pitiful (about 110). It's confusing that some movies are downloadable while others are only streamable (thanks to the patchwork of rights granted by the movie companies). Finally, you can't download a movie onto a laptop for viewing later on planes, trains and automobiles. As copy protection, you can't even watch a CinemaNow movie without an active Internet connection, even if you downloaded it to your PC.

Movielink is much better. Its library includes only about 350 movies, but at least they're recent, name-brand titles from the five participating movie studios and others. (How recent? CinemaNow and Movielink both get movies during what's called the "pay-per-view window" - that is, after they've arrived in the video stores but before they appear on TV movie channels.)

Nowadays, Internet rights are sorted out contractually before movies are released, making them quickly available online after their theatrical run; rights for pre-Internet movies require individual negotiation. New movies, in other words, are likely to expand Movielink's catalog faster than old ones.

In any case, there is no monthly fee for Movielink; you pay only when you download a movie. Nor are you required to be online when you play back a movie; if you download directly to a laptop, you're free to watch it in transit.

Apart from their 24-hour availability, today's movie-download services offer no advantages over TV, video stores and NetFlix.com (a mail-order DVD-rental outfit). Movielink and CinemaNow stand out primarily for their puny selection, poor video quality and overly rigid copy protection.

It boggles the mind that these services don't exploit the potential of the Internet. Any number of improvements could make them more attractive than other video outlets. Online movie stores could offer tens of thousands of movies, dwarfing the selection of video stores. Digital rentals could last two weeks, not 24 hours, without costing the companies a penny more. And there should be a choice of download speeds; people willing to wait longer for superior quality should be allowed to. It is executives, not technology, who keep these services from greater success.

Movielink, CinemaNow and the movie studios ought to put some muscle into improving the concept. That would be worthwhile exercise indeed.