where the spectrum analyzer and waveform analyzer would later appear. Multiple files on the command line or dropped onto its icon were enqueued in the playlist. Winamp 1 Version 1.006 was released June 7, 1997, renamed "Winamp", i.e., with "amp" now in lowercase. It showed a spectrum analyzer and color-changing volume slider, but no waveform display. The AMP non-commercial license was included in its help menu. According to Tomislav Uzelac, Frankel licensed the AMP 0.7 engine June 1, 1997. Frankel formally founded Nullsoft Inc. in January 1998 and continued development of Winamp, which changed from freeware to $10 shareware. Despite the fact that there would be no extra features by paying $10, Winamp's popularity and warm reception brought Nullsoft $100,000 a month that year from $10 paper checks in the mail from paying users. In March, Brian Litman, managing co-founder with Uzelac of Advanced Multimedia Products, which by then had been merged into PlayMedia Systems, sent a cease-and-desist letter to Nullsoft, claiming unlawful use of AMP. Nullsoft responded that they had replaced AMP with Nitrane, Nullsoft's proprietary decoder, but Playmedia disputed this. Third-party reviews found that Nitrane had bugs that resulted in playing back MP3s incorrectly, and that this resulted in unstable tones being added to the playback, and undoubtedly therefore violated the ISO standard. This also means that Nitrane was unlikely to have been based on the AMP software, and was more likely evidence of a hastily written MP3 decoder that didn't concern itself with standards compliance. Version 1.90, released March 31, 1998, was the first release as a general-purpose audio player, and documented on the Winamp website as supporting plugins, of which it included two input plugins (MOD and MP3) and a visualization plugin. The installer for Version 1.91, released 18 days later, included wave, cdda, and Windows tray handling plugins, as well as the famous Wesley Willis-inspired DEMO.MP3 file "Winamp, it really whips the llama's ass". By July 1998, Winamp's various versions had been downloaded over three million times. Winamp 2 Winamp 2.0 was released on September 8, 1998. The new version improved the usability of the playlist, made the equalizer more accurate, and introduced more plug-ins. The modular windows for playlist and equalizer now matched the player's skin and could be moved around and be separated or "docked" to each other anywhere in any order. The 2.x versions were widely used and made Winamp one of