Activision Inc plans to introduce personal computer versions of games it originally designed for Atari Corp’s Atari 2600 system, which was popular in the early 1980s: it will distribute compilations of popular Atari 2600 titles, including Pitfall!, River Raid and Chopper Command, on either floppy disk or CD-ROM for about $30 a time, with the first disk of 10 games in February.