I have a Windows XP Pro box which must run a couple of MS-DOS applications concurrently.
One of these apps is WordPerfect 5.1, the other is dBASE IV.
For some unknown reason, when both of these are running simultaneously, CPU utilization will shoot up to 99% or more, and the process is NTVDM (I know this to be the NT virtual DOS machine, the 16-bit subsystem).
These programs are somewhat quirky in that I had to set up the shortcuts in a specific way so that, when in full-screen mode, the fonts would appear as 25-height instead of 50 (or more).
I did this by first creating two shortcuts to CMD.EXE, and then changed the Layout tab of these shortcuts so that the screen appeared properly. The command line in each shortcut actually runs CMD and then calls the MS-DOS program, for example, "C:\WINNT\SYSTEM32\CMD.EXE /C C:\WP51\WP.EXE"
I need to find some way to make it so that the CPU utilization doesn't go crazy for the 16-bit subsystem, and make it so that the apps will coexist with each other.