upgrading my VGA Display

Dear all,
my pc has a built-in VGA card with only 8MB.. so, very slow when playing movies.. I need to upgrade the memory but the problem is:
I have no AGP expansion slot.. only ISA, and..
the 8MB memory is booked from the pysical RAM, not a separate module belonging to the Card itself 🙁
pls help with all apossible solutions.
thanx :))