I have the same setup ('cept I have an intel core 2 duo @ 2ghz)
(Disclaimer, if some of these suggestions seem 'elementary', my apologies, I'm not sure of your technical level)
1.) First off, do you know the bus speeds of your chipset? (both the front side bus and the memory speed)
AMD systems on laptop platforms currently are not as fast as Intel ones. This could be contributing to why you have lower frame rates that you might have been expecting.
2.) How much RAM do you have?
Vista is a RAM hog like I've never seen. Even after I went through extensive streamlining, I still can't get it to use anything less than 550 megs of RAM. Normal boot (including Aero desktop) you're looking at 750 megs. If your computer is constantly going to virutal memory (located on the hard drive) you'll get what I call 'frame lag' as they pc tries to read from the HDD to get the data it needs to draw the screen.
3.) Also what kind of frame rates are you getting? Are they lower than your previous NWN rig?
I read on Nvidia forums to use ONE of the following locations for Anti-Aliasing settings
A.) Use Windows Desktop Compositing (used for Aero, etc) as it applies this to any graphic application also.
B.) Use graphics card Anti-Aliasing
C.) use Application/Game Anti-Aliasing settings.
They recommend you only use ONE of these methods, disabling the others. The only combination that seems to work is combining A & B. I've experienced problems when I've enabled AA inside NWN. Reducing this might help seeing as you'd have 3 passes for AA on a game that isn't advanced enough to really need it.
3B.) What are the specs on your video card?
I also have an Nvidia GeForce 7600 Go card (the 'real' 256 one, not the 'turbo cache' one where it only has 128 MB on the board and uses 128MB of Ram for the rest, you can tell this by going to system properties in Vista and it'll show how much is on-board RAM vs. System shared)
Depending on your system (determined by your CPU's chipset), you may or may not be getting the most out of your vid card. They may have slowed the cards core clock and RAMDAC speed to be better insync with your system board.
There are a number of utilities on the internet that can help you find out your GPU's specs. Compare those on your computer to what NVidia reports on their website. If there are any differences, that may be leading to performance issues.
The card has the ability to set 'global' settings and then make exceptions for individual applications. I made an exception for NWN to let the game determine the settings.
4.) is this the first time you've tried gaming on a laptop?
I've been gaming on laptops for a while (7 years) and you'll always get lower performance than a desktop, simply because the small size doesn't allow for the latest, fastest and greatest things (mainly because of space and coolling limitations).
Laptop gaming has had huge strides, but still will never be as good as desktop gaming.
5.) Have you tried to play NWN with another Windows OS that works 100% with NWN?
If you have another laptop that has comparable hardware with Windows XP or 2000, try NWN on that and check the results. Keep in mind Vista isn't 100% working yet even though it's been on sale for nearly 6 months now.
WARNING: Don't do this unless you have a restore method in place (spare imaged HDD, recovery CD/DVD, ASR recover set, etc) of your current hard drive.
You could also Dual Boot your computer, but be warned when I did this, I had all kind of problems, but I did get it working eventually.
Some of the issues I had included: crippled Vista install, Crippled Legacy Windows OS install, sound driver problems (because of a Hi-Def sound card chip on my rig by Conextant), SATA driver integration on Legacy Windows OS install CD, conflict with Recovery Partition, BIOS Driver letter confusion vs. Drive letters in OS.
These are all major problems. The last one is really confusing because the BIOS handles drive letters differently than the OS's.
If you decide to Dual boot, please tell me and I'll write out all the steps I had to go through in order to get my vista/xp setup to work.