I thought to improve pc hardware settings to play some good games.
Pc specification now :
Ram = 2gb DDR2
HDD - 320 gb sata
processor - 2.40ghz intel dual cpu
os- windows 7 32bit

So,i want to upgrade my performance. can you guys tell me what should i upgrade so i can play games like : BF-2, gta4, COD 4,black ops, wheelman and others

and my budget is 400$