Not a big fan myself :) I was just experimenting with adobe after effects and this is what my very limited skills could accomplish. Too bad I'm shit at computers and the trial period is over. Can't figure out how to hack the program.
Uninstall the program either with the bundled uninstaller or through the control panel, check your appdata folders for anything the software may have left behind and delete them and then open regedit.exe and delete the offending entries. Should work after a restart. The other method is reinstalling Windows again every time you need to extend the trial period.
The advice was Windows specific. Never had any experience with Macs, but UNIX like systems don't really use a registry in the way Windows does. They probably have the data stored somewhere and the deletion should do the trick, but I can't say where it would be. You could look into proper cracks, which is more convenient than extending the trial over and over and has the same end result. You use the software how you like without paying for it.