You can try this download:
http://www.firoball.de/index.php?show=19But there are many problems under Win2000 and Win XP.
On XP systems the game usually crashes when entering level 1 (starting new game). Level2 and Level3 work fine.
The DOS executable has problems as well. Sound most likely won't work and sometimes it runs very very jerky.
So what you can do is finish level1 with the DOS version, save at the start of level2 and then continue with the Windows version.
However, timing was not very accurate in A3, so there are several timing problems when running on a newer PC.
If you can get a Win9x PC or an old Dos PC - run it on this machine.