I've been having problems with shadows since I got my Nvidia XFX GTX 280 (standard edition) graphics card. The shadow edges are always jagged and not smooth. I've tried updating the drivers and increasing/decreasing the antialising option in several games but I still encounter that problem.
A more serious problem I've been having is on Call of Duty:World At War (might I add, amazing game!). I've finished the game a few days after the release and I don't remember having any problems with the games graphics.
So I got the urge to play the game again and I've had really bad graphics problems in any stage which has water in it (see image)
My system specs (all at stock settings):
Intel Quad Core Q9300 2.50Ghz
XFX 780i 3-way SLI
2x2GB Corsair DDR2 800Mhz RAM
WD HDD 500GB Green Edition
Nvidia XFX GTX280 1GB GDDR3
Windows VISTA 64-bit Ultimate Edition
Then open up Rivatuner and you will see a section called "Driver Settings" with "Forceware" and "customize" and a list of option when you click the arrow beside "customize".
Then you just select system settings which is the first graphic that looks like a video card, and a new window will appear. Select the box "Enable driver-level hardware overclocking" and then tell it to detect your settings without a reboot. Then it will load up your clockrates for your core, shaders and memory. Maybe try seeing if they match what your card's standard clocks should be, and if they do, back them off maybe 25MHz at a time, then go into your game and see if it's any better.