GT540M is much better than 4 year old 8800 series card.
And yes, you should NORMALLY get your drivers from nvidia.com, even if they are mobile cards. Dell usually just repackages nvidia drivers anyhow and they are usually months behind nvidia. I know that cause I have an old XPS laptop as well, with nvidia dedicated chip, and I gave up on "dell drivers" long ago.
HOWEVER...
Sadly, it seems that nVIDIA themselves dont have an official driver for your GPU right now, since it is so new. So you gotta use what came from Dell, for now. There are a lot of pissed of people without an actual driver on official nvidia forums. (
http://forums.nvidia.com/index.php?showtopic=195897) I mean, that f***ing sucks, how can they sell a laptop without proper drivers.
You can also (at your own risk) try installing the latest nvidia driver anyway.
Also try this site, they usually have specially modified drivers for new laptop chips (
http://www.laptopvideo2go.com/) YOUR BEST BET IS THIS SITE!
There are people complaining about your chipset as well here:
http://forums.guru3d.com/showthread.php?t=339445 and here
http://forums.nvidia.com/index.php?showtopic=194614 and here
http://forums.nvidia.com/index.php?showtopic=191054
I know this is the last thing you wanna hear right now, but you`re screwed. With the current drivers, there are a lot of problems, and nVIDIA or DELL don`t seem to care.
If the newest video drive doesnt work (whenever it is released, it is up to nvidia right now), try getting the latest chipset driver and latest audio driver.
If that doesn't work, then the game just doesn't like your GPU. Sucks, but all you can hope for is a patch. Which, given Paradox's previous games history, is unlikely.
Sadly, it seems that nVIDIA themselves dont have an official driver for your GPU right now, since it is so new. So you gotta use what came from Dell, for now.