This information was provided by Claris Corporation on 16 March 1998, and incorporated into Apple Computer's Tech Info Library.
b) Chances are the illegal operation error occurred because of a memory conflict in your system. This may result because there wasn't enough memory available for the specific application being used. Everything about Windows 95 is memory related. If you installed Windows 95 using the default configurations, your machine is using virtual memory. You can check this by going to settings from the start menu/control panels/ system/performance/virtual memory. Select "let me manage my own virtual memory settings". The virtual memory settings should be: the minimum swap file size should be the amount of memory that you have installed and the maximum swap file size should be set to your memory installed doubled. For example, on a machine that has 16mb ram installed, your minimum swap file size should be set to 16mb and your maximum swap file size should be set to 32mb.
The best defense against the Illegal Operation Error message in Windows 95 is maintenance. If you can make sure that all of the above steps have been performed, you can reduce the probability of getting the dreaded Illegal Operation Error message in Windows 95.