#MS Encarta
THe Groliers is pretty good, and I'm most impressed by the fact that I
had it under its first incarnation and when they brought out the new
multimedia Windows version (bigger, jazzier, etc.) they sent upgrade
notices just like any other software company and did a nice reasonable
upgrade.
Alas, most CD ROM software companies have no upgrade policies at all.
If you really want an OK encyclopedia, Groliers is fine. Neither it nor
Encarta nor any other disk-based one matches my 20-volume Britannica,
though, in terms of information available.