I'm having problems running GNOME Shell with my NVIDIA 7025/nforce 630a (on-board). The animations don't run smoothly when I configure my BIOS to give 512MB to the chipset. The only solution I've found is to change the shared RAM to 128MB. After this, the animations run well but I can only use 128MB for some applications.
You have a combination of things that can be improved. NVIDIA 7025/nforce 630a on-board video controller is "at best" a minimal performer. Recommend upgrading if at all possible.
AMD processor is a 2MB/AM3 which is not bad but if the board is a AM3 then there are other pieces that are faster than a AMD Athlon 240x2.
Mostly the GPU suffers from the nforce 630's performance. This is probably where your issues stem from. read specs here
Now all that being said. I would recommend Lubuntu as the system of choice.
