PC performance in new games....

i have noticed poor performance on new games a which are graphically better......i think that my pc is somewhat up to par and should be running them better.....what i think it is is memory but ill let you guys look at my specs and lemme know.......in the middle of a game like Ghost recon when th action gets intense the pc begins to struggle and the gameplay is very choppy and poor.......i have come to think that it can be only 2 things......memory or harddrive for they are the 2 oldest componets of my pc......

amd athlon 950mhz
via k133 msi motherboard
geforce2 mx 32mb
160mb ram pc-133------>do i need more?...will 512 more help?
15gb 5200rpm maxtor---->is this slowing me down?

the rest of the pc is basically normal nothing else specail ....also nothing is overclocked.......so i am thinking that i need more ram because i know that the performance i am getting on game now is not as good as i should be getting with my cpu and graphics card.....

any suggestions?...thx