The Disney Animation Studio program goes way back to the days of the Commodore Amiga Computer, even though there was also a version released for MS-Dos/Windows 3.1; I never came across the latter so I wouldn't know if you can run it on a more modern Windows version. The wonderful thing with this program was the onion skin function, that worked like a traditional animator's light tish; in the Netherlands, even professional animation assignments were created with ths program; if a wobbly sort of line and style are required, you can produce a hell of a lot more footage per day then on paper - or at least, I could. The studio that used to work with Disney-TAS and D-Paint in the early nineties has switched to PC's and NewTek's Aura program, that brings the same sort of animation techniques into the new millenium. Apart from the onion skin mode, it also supports unlimited animation layers and painter-like coloring tools (with high enough resolutions to go beyond simple AVI's, and go cinematic instead) and can be used as a compositing tool as well. Since they advanced to higher versions, Aura 1.0 was a PC-Magazine giveaway mid-2002 (On the august-edition of Digit, to be precise), and a free download for a while; it seems to have been removed from the Newtek-site, though. I'm considering using it as my main tool for an independend animation short; I've seen it used professionally on a range of productions in a range of styles. Good Luck