Ehm... read the error message again 😀 The collector's edition of X-Com games have been rewritten to operate in Windows instead of DOS. So you can't run them through a DOS emulator, nor through 'real' Dos - you have to run them through windows.

I must admit I have absolutely nothing to complain about either. I played Rings of Medusa for the first time in 10 years yesterday, and had no problems whatsoever (well, apart from sucking at the game now :) ). DOSbox is absolutely brilliant work, and I can say that after trying out a few emulators …