Support for MS-DOS based programs is fading at Microsoft. Windows Vista does not natively support full-screen DOS mode for MS-DOS based programs. Attempts to execute ALT-ENTER in DOS programs will result in a message: “This system does not support fullscreen mode”. Several people have noted a workaround is to fall back to Windows XP drivers instead of the built-in Windows Vista ones (Vista Starter Edition apparently doesn’t use WDDM drivers due to its lack of Aero support and therefore does not have problems runing DOS programs full-screen).
It also appears that expanded memory (EMS) support is also gone, although this post from Matthew Braun from Microsoft states you can get it back by doing the following:
You can change these settings by running explorer as Administrator or you can also change it from Safe Mode. To run explorer as Administrator, open up a new elevated command window by right clicking cmd.exe -> Run as administrator, then open Task Manager and End Process on explorer, then from the elevated command prompt type explorer.exe (DO NOT EXIT TASK MANGER). Explorer is now running elevated, navigate to C:WINDOWSSystem32command.com and right click -> properties, proceed to change the setting in the memory tab. After you are completed to return explorer to a standard user process context goto task manager and end the explorer process, then goto File->New Task(Run…) and type explorer.exe, explorer is now running in a standard user process.
The other option of course is to run your legacy OS in VPC 2007 under Windows Vista.
– Soli Deo Gloria