>I am using a vfp 3.0b application. I always have a this
>error about 3 times a days : VFP300 ERROR, this program
>make a Illegal Instruction : close or details. VFP300.ESL
>is install in the c:\windows\system directory.
>Could someone help?

It sounds like foxpro can't find the library file it needs. This could be for various reasons:
1 - the within foxpro can't find the library file. the esl file maybe in the wrong directory or not there.
2 - the *.esl file is corrupt.
3 - memory problems on your PC. Something maybe conflicting with the foxpro or app setup.

reinstalling foxpro or the app may help.