Laptop graphics adapters are slightly different to those usually found on desktops.
In a desktop machine, the graphics card usually has its own onboard memory, which is one of the features to look for when buying a card. The computer will download graphics information and drawing instructions into that memory, and the graphics card (which is actually an extremely powerful computer in its own right) can process that to generate a display.
In some ways, the memory size is a measure of the card's capabilities, along with GPU speed, bus type, bus speed, etc.
In laptops, the graphics card is usually integrated into the mainboard, and does not have its own memory.
Instead, it steals/shares memory from the main computer.
This means that your main computer has less memory to play with.
In your case, it's stealing 128Mb.
So if you've only got 512Mb in the machine altogether, that means up to a quarter of your memory could be used by the graphics card, leaving a lot less for the main computer to use.
It may be possible to adjust the 128Mb share size by changing a BIOS parameter, typical laptops can go as low as 8Mb or as high as 512Mb.
You need to login before you can answer.