How should i upgrade my computer?

Well you don't say how much RAM you have... So for a start you should get at least 2 gig of dd2 800mhz RAM, a graphics card with around 512k of memory, and a bigger processor around the 2.5 gig to 3.2 gig mark that will set you up with a good enough computer and it will only be around the $500 to $1000 range but it will depend on what brand graphics card and RAM you buy