Thanks for all your replies...
Currently, my computer has an Intel 845 AGP chipset, 32 MB ATi Rage 128 Pro graphics card, an 80 GB Seagate HD, 128 MB RAM. My Monitor and Hard drive are brand new and other peripherals are in good condition. I am planning to buy a new CPU. What hardware from my present CPU can be used in the new CPU? And also I wanted to know whether an upgrade of the CPU or a new CPU would be better. I dont want to buy a new monitor, speakers system, mouse, keyboard, and a hard drive. So what should be the cheapest and the best configurations for a CPU for around 320$ ?