Well there are some ways through which you can increase memory of your graphics card for mining for example;
1. You can start by totally clean of windows.
2. or you can also reset you PC to clean your Windows system.
3. Regularly clean system tray. it will speed up your system.
4. Always have updated graphics cards driver.
5. Always have updated minor program.
6. You can over clock your card like at 5 % at least using over clocking utilities.
7. Keep you rig clean and provide sufficient air to prevent it from overheating.
These are simple methods which surely increase memory to a great extant.
EDITED: No links to 3rd party web site please
