|Dedicated Video Memory is generally what the video card is built with.|
You might have an option in your BIOS if you are running internal Video (on CPU or ChipSet) for reserving a certain amount of the memory for video but it is unlikely to make a significant difference.
Please tell us what machine you have (Make and model). Desktop or Laptop? What Graphics?
You have to be a little bit crazy to keep you from going insane.