TLDR: It's not supported, it's even unwanted and the performance is likely to be poor. If you want to safe battery life, I'm not sure switch GPU's is going to make an enormous difference either. So sorry, but I think it's impossible.
Here's nVidia's take on the problem:
Question
Does the Apple Macbook Pro (Late 2008) support NVIDIA's Hybrid SLI® technology?
Answer
No. NVIDIA Hybrid SLI technology for notebook computers allows a motherboard GPU and a discrete GPU to work together for extreme multi-GPU SLI performance when needed (called GeForce Boost mode), or use just a single GPU for low power consumption and long battery life (called Hybrid Power mode).
Apple's Macbook Pro (Late 2008) does feature both the NVIDIA® GeForce®9400M motherboard GPU for everyday computing and the NVIDIA® GeForce® 9600M GT discrete GPU for high graphics performance. You can switch between the Geforce 9400M motherboard GPU (called "Better Battery Life") and the Geforce 9600M GT discrete GPU (called "Higher Performance"), but you cannot use both GPU's at once in this implementation.
Apple's hybrid graphics technology is supported under the MacOS X operating system version 10.5.5 and higher only. When running Microsoft's Windows XP™ or Microsoft's Windows Vista™ using Apple's Boot Camp, the system locks into higher performance mode which uses the Geforce 9600M GT discrete GPU for all graphics related tasks and can not be changed to use the Geforce 9400M motherboard GPU for battery life mode.
For more information on Hybrid SLI technology, click here: Hybrid SLI
For more information on the Apple MacBook Pro featuring NVIDIA technology, click here: Apple MacBook Pro
Furthermore you have to be using Vista or Windows 7 to even be able to use it:
Q: Which OS supports Hybrid SLI?
A: Hybrid SLI is supported only by Windows Vista. It is currently not supported with any other operating system.
Though Microsoft seems to think Hybrid SLI is a bad thing, because Fudzilla claims that it won't be supported for Windows 7. This makes it even more unlikely it will be easy to find a hack for this...
In Microsoft’s Guidelines for Graphics
in Windows 7 document, which was
released yesterday, Microsoft outlined
its feelings about hybrid graphics,
stating that ‘Windows 7 does not offer
native support for hybrid graphics
systems.’ Not only that, but Microsoft
added the reason for the decision
saying that hybrid graphics systems
‘can be unstable and provide a poor
user experience,’ and that it would
‘strongly discourage system
manufacturers from shipping such
systems.’ Microsoft also added that
‘such systems require a reboot to
switch between GPUs.’
So if Windows doesn't handle the Hybrid SLI very well, then you won't get any performance boost either:
When applied in PC notebook SLI Hybrid
technology does not provide the
expected performance level so far, as
both chipset and GPU spend a lot of
time to exchange data and 2D/3D
rendering are not really boosted.
However, as a recent technology, it
will improve over time and its GPGPU
power might be important as well.
Just looked on Dell.com for you and it does not look like Windows 7 is supported / drivers are not yet available.
If you look at the driver page (Vista x64) / driver page (Vista x86), you may have luck with the Vista drivers, but obviously I can't guarantee it.
I see no drivers directly saying light control, but there are a few optional packages such as what is listed as "Dell utility - Notebook system software" that may have controls in for what you want.
Best Answer
No, there's no compatible ALS driver for Win 7 x64 yet. Many have asked, none have found so far.