Google and download Driver Cleaner Pro. It's freeware. Then download the latest drivers (perhaps XtremeG would work, you can get them from www.guru3d.com
) to your desktop. Use the Remove Programs control panel and remove your current nVidia drivers. Then restart and start up in Safe Mode. In Safe Mode use Driver Cleaner Pro to remove any remanants (those are the files that might be corrupted). Restart and install the new drivers and presto, you should be good to go.
If it still blue screens, then it is very possible it might be a RAM issue. DAoC and other games are very RAM intensive so you will most likely expose any errors by simply playing. I had a RAM issue on my old desktop and it would run perfectly fine unless I played DAoC, then it would blue screen at random intervals. Turned out my motherboard didn't support DDR400 past 512 ram, and I was using a gig. To see if its a ram problem, which can just be some errors on a stick you received from dell or perhaps an upgrade, download Memtest 86+ (just google it) and then create a start up disk with it. Before you go to bed leave it checking all night. After about 8 hours or so you can be assured that you either have or don't have any errors.
If that doesn't work, then come back here and tell us your progress and we'll advise you what else you can try. I'm pretty sure its one of those two problems tho... actually I'm very sure.