AVGcensor is the promised program to remove the naughty-type adult bits from AIR and Kanon.
If you bought the adult version and then wished you hadn't, this program should solve your problems (and make it safe for your mum and/or kids to play the game too). If you haven't bought the game yet, you should be aware that this program does NOT turn the adult version into the all-age version; the latter features all-new graphics that are not included in this package.
Anyway, for those as wants it, you can get the thing here
(277 kb). Includes source code for perverse types who insist on not using Windows. :p