upgrade to i5. The e5700 is a 3 year old dual core cpu. If you get a new quad core i5 it will easily last 4 years or more. However, GPUs get outdated faster.
But I noticed you only have 2gb RAM and it is ddr2. If you got a i5 you'd need a new mobo and new RAM. Are you willing to get new components? And maybe a new GPU this year or next year?