Just a few days ago,I've got a new computer:
CPU: Intel i3 530
Video Card:Nvidia GTX460
Memory:DDR3 1333 2G*2
OS:Win XP SP3
I think this computer would run Oblivion smoothly,but it seems that I'm wrong.
I'm running the game with no AA/AF,HDR lighting at 1280*1024.
I can get ~50 FPS at most outdoor area,but once I get to the IC market,my FPS stuck to ~20.Which is almost the same with my old computer( 8600GT&AMD Athlon 5000).
Also,my game lags every a few minutes.
Can someone tell me what is wrong with it?I have mods including OOO+MMM and a few texture replacers,but it runs only a few FPS faster than my old computer in some areas just make me fell weird.

I'm running an i5 760 and AMD 6950 overclocked.
I get around 25 FPS in the Market Place.

Such is the way of Oblivion. Chances are it's more a CPU bandit than a graphics one though.

The Intel Core i3s are not the most powerful CPUs out there. And since there are many NPCs in the area, you will see a FPS drop. (Also you are limited to how much RAM you can use because you are using a 32 bit OS.) Even on my PC it drops to about 35 average with QTP3/OOO/MMM/Frans