Can i play gta iv on my pc having 2.4 ghz processor 1gb ram 256 ati radeon video

Not a chance. I've got a Phenom II X4 running at 3.6ghz and a GTX460 graphics card and I can only get 45-55fps on nearly maxed settings. The game will use all of my GPU ram (1GB on its own), and usually 2-3GB of normal ram with the GPU pegged @ 100% load and ALL CPU cores @ 60-75% load.

Minimum needs: A very high clocked dual core or quadcore, 4gb ram, 1GB ram GPU (GT240 will run the game at lowered settings and playable framerates).

Thats from my personal experience with the game and hardware.
 
Do you have a place similar to Newegg that you buy individual parts from?

An Athlon II X4 or Phenom II X4 would be a good value for your dollar if your trying to play a game like GTA IV, seeing it likes multicore so well.
 
Well In Pakistan You Can Get the CPU you Mentioned should be around 10 thousand rupee. It also depends up on the market from u are purchasing. but These are not exact specifications you mentioned. the model number and brand matters most. Would You like to tell the budget and for what purpose you will be using your machine?