Several technology producers already offer copy-protection systems that media companies can use when they sell their content in a digital form.

Ultimately, technology executives say, the problem is a pragmatic one: it may simply be impossible to devise a copy-protection system that cannot be cracked.

Then last week, the programmer, Dmitri Sklyarov, was arrested by federal agents at a conference in Las Vegas, where he described how to crack copy-protection system.

Others came with elaborate copy-protection systems such as Zool's circular code wheel, or even a hardware dongle (although these were generally more common on expensive non-game software).

It cannot, however, play songs you've bought from the iTunes Music Store; Apple continues to keep its copy-protection system to itself.

The game contains a copy-protection system that asks the player to consult the game's manual to find out what star system to warp to on the navigation map.

Technically, overriding the copy-protection systems on the software to copy it onto more permanent storage media is illegal, Mr. Kahle said.

This flailing, of course, is exactly what the music-downloading business did before Apple broke through the chaos, set the price standard at 99 cents a song and included a copy-protection system.

It also suggests making it an infringement to thwart copy-protection systems, like encryption, that copyright owners use to protect their work.

ARccOS is a copy-protection system used on some DVDs.