How can I turn on the Intel HD manually?

For some weeks my MacBook 6.2 does not switch to the integrated graphics adapter (Intel HD). This is especially crucial when I work on battery (which happens quite often). I guess the runtime could be enhanced when it would take the HD adapter for display.

I checked that it automatically changes the graphics mode. I am running Snow Leopard 10.6.8.

I recently installed 8GiB RAM (not from Apple). Could this probably related to this issue? Actually I do not want to downgrade or use the expensive Apple RAM.

So, how can I manually turn on the internal graphics adapter?

gfxCardStatus will let you choose which Graphic Card to use. It has three modes:

• Dynamic Switching: An alias for the built-in automatic graphics switching feature in OS X.
• Integrated Only: Forces the more battery-friendly graphics on and disallows automatic switching.
• Discrete Only: Forces the more power-hungry graphics on and disallows automatic switching.