Welcome to LQ
Take down services you aren't using. If you aren't running a mail server stop it, if you aren't running a web server, stop that. Check out a few threads around on stopping services not in use.
Other options for speed increase:
* Use other window managers (fluxbox)
* Use other applications
* Do more things in a command line (not too many people are fond of that at first though
* Recompile your applications for your hardware (you can use SRPMS to do this so you don't actually have to use the source, check out 'man rpm' for more info on that)
* Recompile your kernel to streamline what gets loaded (specific to your hardware)
Grab the NVidia drivers from www.nvidia.com
and install them, that'll help with speeding up X a bit.
Services though, that seems to be the number 1 thing to improve system performance.