isapi and Apache

I wrote an isapi with VC6 and it work fine on IIS. When try to run it on
Apache 2.0.52 it returns "the page cannot be displayed" message. I have set
AddHandler directive to "isapi-isa .dll" and ISAPIReadAheadBuffer to 4G.

I would appreciate if someone could provide some additionnal settings I
missed in documentation or other settings not mentionned in Apache docs.

Thanks, Jacques