Newcomer Aimster is taking two of the most popular activities on the Internet, file-sharing and instant messaging, and combining their features to provide mainstream users with secure file-sharing software. But in doing so, Aimster also comes under the gaze of two powerful forces that have aggressively gone to court to defend their turfs: The recording industry, and America Online. The free software download draws on AOL Instant Messenger's buddy lists to create groups that can share files through Gnutella's file-sharing technology. Gnutella is an open source file-sharing technology similar to Napster, which was developed by AOL's Nullsoft unit but now lives on independently. Aimster has been downloaded 4,500 times since its launch Tuesday, according to the company. AOL's Instant Messenger service has an estimated 40 million to 60 million users, with millions of people engaged in file sharing. But unlike the Napster service, where music files are traded in a public forum that the recording industry says robs them of sales, most AIM users participate in private exchanges. In essence, Aimster users are sharing files with friends, a distinction that the company believes will make it immune to Napster-like lawsuits. Under the Audio Home Recording Act, consumers can share music for personal use with family and friends -- the people who are likely on buddy lists, said Johnny Deep, spokesman for the company. "The mainstream doesn't want to share files with everyone, and we're targeting them instead of the ten percent of early adopters that are willing to share with everybody," Deep said. Aimster could also fall foul of AOL, which has aggressively blocked non-licensed companies from using it's Instant Messenger service. Deep said that technologically AOL can't block Aimster. An AOL source said the company is still trying to figure out the technical ramifications of Aimster. No action has been taken against the company, the AOL source said. According to Chris LeTocq, research director at Dataquest, Aimster may be shooting itself in the foot by limiting file-sharing communities. "This is yet another wrinkle in the insatiable demand to take advantage of the group nature of the Internet," said LeTocq. "Napster's growth was because everyone had access to everyone else's files. Aimster makes file sharing exclusive, creating a barrier to entry." But Deep said that the software also allows users to browse and search the larger Gnutella network in addition to their IM buddy lists. The Aimster software is part of the patent-pending intelligent switching technology that the company's 14 developers have been working on for 15 months. The software currently doesn't work well behind firewalls but the company will be releasing a new version to fix that by the end of the month. Ben Charny contributed to this story. Take me to the MP3 Specialv What do you think? Tell the Mailroom. And read what others have said.