And the amount of available RAM for Video while being one isn't an overriding one. Aero require at least 64 MEG of RAM on the Video Card and some better than normal Video cards to work. So you can try going into BIOS and setting aside 64 MEG of RAM for the Video but this may not have any effect depending on the Video Chip that is built into the NB in question.
By allocating more RAM to the Video you may actually slow down the NB considerably. Every NB that I've seen Aero running on has it's own dedicated 64 MEG Ram Video Module built in and doesn't rely on shared Memory or Shared CPU cycles to generate the Video Signal.
Col