Oblivion fps maybe low??

Hiya people, I want to know if I have low FPS with TES:Oblivion. I maxed out all my settings except for resolution (1280x960). When I'm at cloud ruler temple, just walking up the stairs I get 37FPS and inside I get 17FPS when looking at the fireplace with my new 8800GTS 320MB. In towns like the town near cloud ruler temple I sometimes get 16FPS or lower and in some parts it goes higher. I checked the game yesterday at a friend of mine and it seemed to work very smooth with his 7800GS, game setting maxed out resolution 1280x960 and his OS is XP. Maybe it can be my OS. I want to know if this is normal cause I know oblivion is a heavy game that requires a very good pc. My pc specs are:
Amd Athlon 4200+ X2 @ 2.2GHz
MSI K9N neo-F
2x512MB DDR2/800 Nanya & 2x1GB DDR2/800 (dual channel)
XFX 8800GTS 320MB
OS Windows Vista Ultimate

Vista eats RAM. And I guess the Ultimate is even "worse". You probably need another gig.

And you probably wont get dual channel, mixing 512mb with 1 gig RAM sticks.

Download CPU Z and check if it says you have dual ch?

Also, it will depend on what quality settings you're using?

Besides, the Nvidia drivers for Vista is'nt top notch.

Have you made sure you have a defragged harddrive(s)?

No spywares running?

I do have dual channel, I checked it with Everest Ultimate edition, I tried two combinations, first:
Slot 1 512MB Slot 3 512MB
Slot 2 1GB Slot 4 1GB
It said active mode single channel then I changed the combination to:
Slot 1 & 2 512MB
Slot 3 & 4 1GB
and it said active mode dual channel.
My pc doesn't have any spyware and the HDD's are defragged. I think I'm going to install XP and vista or only XP then.

Do you btw have Oblivion, cause I see you have a 8800GTS too. If you got it, what FPS do you get?

When I play Oblivion, fps is always slower indoors, and when lots of npc's are around. Does it only happen it that one place, or all over?

It happens all over. I have noticed that other games also don't work really like they should with a new videocard. I'm just gonna install XP again this weekend, see if this resolves it.

I still have very bad FPS, I notice this with games like Company of Heroes, NFS Most wanted, Oblivion, Battlefront II. I checked the internet voor benchmark tests with a XFX 8800GTS 320MB and they are showing higher results than my computer. Like CoH, when I use default settings (most of settings are medium and resolution 1024x768) I get like 50 FPS and when I press alt to lower the camera I get 20 FPS. Does anyone know what my problem is cause this is really getting on my nerves because I thought a new videocard would give me better game performance but it didn't :S.