Get new drivers for your Graphic and Soundcard, also make sure you have the latest drivers for all of your harware ex. Chipset.
Make sure you do regular maintenance on your computer. For example Defrag your harddrive, clean out the registry with a register cleaner, be sure to run ad-aware to remove any spyware, run a anti virus program etc. The list goes on.
If you want to know more about your computer and what you need to do to keep it running smooth and troublefree. Checkout the "Tweaking Companion" over at TweakGuides.com
That 166 pages long guide cover most if not all areas of your computer and what you can do to make it preform like it was new. It also focuses on freeware so money doesent need to be an issue.
Hope you will be able to play soon