Resolving Rundll, Rundll32, and Mmsystem.dll Error Messages in Windows 98 or Me

This document pertains to PCs with Windows 98 or ME installed.

One of the following error messages is seen in Windows 98 or Me:
"RUNDLL - This program has caused an illegal operation and will be shut down."
"RUNDLL32 - This program has caused an illegal operation and will be shut down."
"RUNDLL caused a general protection fault in module MMSYSTEM.DLL at ...."
"RUNDLL32 caused a general protection fault in module MMSYSTEM.DLL"

Correct the system.ini file

To correct this problem, prevent mmsystem.dll from loading by doing the following:
Click Start, Run, then type the following into the Open field: System.ini.
Click OK. The file should open in Notepad. If it does not, then a window will appear titled Open With. Select Windows Notepad and click OK to continue.
If a line similar to drivers=mmsystem.dll is under the [boot] section, type a semicolon (;) at the beginning of that line.
For example, ;drivers=mmsystem.dll wndrv.dll
Type the following new line under the [boot] section:
drivers=mmsystem.dll
Click File, and then Save.
Close all open windows and restart the PC.
Related support
Microsoft Support Article Error Messages in Rundll32 or Mmsystem.dll. (in English)