AMD athlon x2 4400+ (2.31 ghz)
Zotac geforce GT 240 amp! 512 mb (GDDR5)
windows 7 home basic 64 bit
Now my game gives around 13 fps on 1000 x 8** pixels and medium graphics. I can only get to medium texture setting for some reasons and it doesn't go any high and it doesn't even use full vram...Now when i go to systemrequirementlab it says even in recommended that my graphic card is fine but my cpu is low as well as the ram but why my graphic card only go upto medium graphics??? when it can go upto very high here in this benchmark.
Technically you are under the minimum requirements anyway. According to the Rockstar site your CPU is 100Mhz short of the minimum and you barely have enough RAM. The GT240 kind of a joke for gaming too as it performs about as well as a 9600GT which was a mid-range card released over 2 years ago.
If you really want to play GTA4 at a reasonable speed then get a quad core CPU with at least 4GB of RAM. Your video card should be good enough I suppose but it would also be worth it to consider a more modern mid-range card like the AMD 5770.
Upgrade your ram to at least 3gb and get a better cpu, a 65w edition or better a 45w that is clocked higher than your current that your board supports. If you are not overclocking your cpu and have a board that does have options to overclock I would explore that in the mean time. Ram first.