MS-DOS apps cause NTVDM to 99% utilization

Posted on 2003-10-28
Last Modified: 2008-06-02
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.  
Question by:Zoplax
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Expert Comment

ID: 9633826
Do you see the utilization high only while these programs are running or even with them

I would suggest 2 things

One if they are high without the applications running , check for spywares

Spyware/Adware removal tools:

SpyBot-S&D :

Ad-aware :

Trojan Remover :

HijackThis :

KL-Detector  :

X-Cleaner Free  :

If they are high only when the applications run, reinstall them and check to see if they would solve


Author Comment

ID: 9633877
Thanks Sunray, I've already run SpyBot on this system and it cleared a few traces of spyware, but problem still occurs.  

Also there is nothing to reinstall with the MS-DOS apps; they are shortcuts pointing to the application files which are on a network server.

The CPU utilization seems high only when these apps run at the same time, not any other time.  

Accepted Solution

GloomyFriar earned 250 total points
ID: 9633962
It's normal. Try to lower priority for the apps.
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Author Comment

ID: 9634801
Thanks GloomyFriar, it turns out that there is a known problem specifically with WordPerfect 5.1 which causes it to eat CPU.

I researched and figured out a way to get around this.

First of all I created a batch file which simply runs WordPerfect, for example,


Next, I created a second batch file which executes the C:\WP.BAT one above, preceded with the START command,

  START /LOW "WordPerfect" C:\WP.BAT

This causes the batch file to be opened with LOW priority, and with "WordPerfect" appearing as the title of the dialog box.  The EXIT command in both batch files automatically closes the user out of the sessions once they exit WordPerfect.

The end result is that WordPerfect runs, and may still appear with 99% CPU utilization for its associated NTVDM.EXE instance, but as soon as any other application with a higher priority runs, Windows compels WordPerfect to relinquish its hold on the CPU in favor of that application.  

Author Comment

ID: 9634862
Whoops, I should add that I changed the registry so that each 16-bit program runs in its own NTVDM.EXE process.

I changed HKLM\System\CurrentControlSet\Control\WOW\DefaultSeparateVDM from "no" to "yes".  Reboot after making this change just in case.

Expert Comment

ID: 9635691
I'm glad to help.

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