NEW YORK (CNN/Money) - Almost two-thirds of Americans with Internet access have at least one digital music file on their computer but most downloaded music is held by a relatively small group of users, according to a study released Thursday.

Not surprisingly, most downloaded music is on computers used by teenage boys and young men, according to the study by the NPD Group, a consumer research firm that tracks computer use online by about 40,000 computer users.

The study estimated that only 8 percent of downloaders have more than 1,000 music files on their computers. But those large users account for about 56 percent of an estimated 11.1 billion downloaded files, according to the group's research. And the average number of music files held by those heavy users is 2,300 songs.

Another 18 percent of music files are held by another 8 percent of the downloaders with 501 to 1,000 music files. That means that nearly three-quarters of all music files can be found on 10 percent of computers that have more than 500 music files, according to NPD.

The survey comes just two days after the recording industry filed 261 copyright infringement lawsuits against users it charges had distributed at least 1,000 music files apiece, on average. The NPD Group said its survey found that the Recording Industry Association of America's (RIAA) strategy of legally targeting large users is a good one.

"There clearly are a small percentage of users who have taken advantage of filing sharing services to compile massive libraries," NPD Vice President Russ Crupnick said in a statement.

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"The RIAA's focus on those sharing the most files makes sense, because this group provides the most egregious example of one of the music industry's most pressing business issues -- copyright infringement."

The typical active music downloader is young and male. NPD found that nearly 28 percent are males aged 18 to 25, and another 15 percent are teenage boys, 13 to 17. Girls and women from ages 13 to 25 make up another 18 percent of music downloaders. Only about one in five are older than 36 and less than 5 percent are older than 50.

Overall, about 40 million households had at least one music file downloaded to the computer, which Crupnick said is not necessarily a bad thing for the music industry. He said it shows a large base of potential users for the paid music sites endorsed by the recording industry.

While NPD couldn't estimate how many music files had been legally downloaded from those sites, there is a growing awareness of those sites by those surveyed by the firm, he said.

"About 2.5 percent told us they had bought something from those sites, and what these numbers say is there are tens of millions ready for the digital revolution," he told CNN/Money. "There is a recognition on behalf of the recording industry that this is a legitimate and high opportunity distribution channel for music."

The survey also found that two-thirds of all music downloads came from file sharing, with the rest coming from taking songs directly from compact discs. Among the most popular "peer to peer" file-swapping services, the survey found Kazaa the leader with 21 percent, followed by WinMX with 5 percent usage.