well you'd have to go higher than just 2ghz to notice a real improvement, but it still probably wont make it smooth like you're thinking. It's more than likely because you have only 512mb of RAM. Mine does that same freeze BS, but it's cause I'm OC'ing my RAM and CPU as well, soo in my case I just need to lower the OC a little bit.
BTW: You might get more help on overclocking if you put it in the 'Overclocking' section and not hardware
Moving it there. Read the sticky at the top of the OC'ing thread