I hate to be the guy that say, "Yeah, what she said," but XxCourtneyxX is right.
Ubuntu
Let me try and give some reasons that she hasn't covered already.
* Choice of desktop environments. Ubuntu supports Gnome, KDE (Kubuntu), and Xfce (Xubuntu) as "native" desktop environments. So, no matter which one you end up liking the best, it is easy to install and well-supported. And it is easy to install more than one and have a choice.
* Huge repositories. Literally, every Linux application you could ever want is available through the repositories. I bought an Ubuntu book with a chapter on compiling from source. The example the author gave was a program that -- he admitted -- you would not need to compile from source because it is in the repositories. He couldn't even come up with an example of a program that wasn't there.
* Synaptic package manager. Makes accessing those repositories and installing/uninstalling new software a piece of cake.
* Great community support. I know, XxCourtneyxX already said this. But it should be repeated. Ubuntu has a very large following, so it is easy to get help. It has excellent forums and excellent community documentation. It even has a site very similar to Yahoo!Answers, but just for Ubuntu.
So, yeah, Ubuntu. I would get several live CDs for various *buntus and Ubuntu remixes, along with some other distros. Try them. Figure out what you like the best (remember, most full-featured distros perform pretty slowly off of the LiveCD).
One caveat: I cannot find your graphics card on the list of Nvidia cards supported by Ubuntu ( http://us.download.nvidia.com/XFree86/Linux-x86/169.12/README/appendix-a.html ). But the list is two releases out of date, so there might be no problem there.
Hope this helps!