Want help with PC configurations-urgent
 

i want to upgrade my pc....i have pentium-4,160 gb hard disk,256 mb RAM.. which 1 is better dual core? core 2 duo ? or core 2 quad... i want to speed up d apps ..as requiremnts r incrsng,,need for more softwares has led my pc to go slowand hang up in d mid ...... plzzz help...