Dear Venkatesh,
Buying a PC is till a tuff job specially when you have got more than 50 good motherboards and a dozen processors in front of you.
Here are some suggestions from my long hardware career:
If you engaged in gaming and multimedia applications, AMD Athlon 64 3000+ and above is the best. If you can spend 2K more go for the Athlon 3200+ Socket 939 processors.
Regarding motherboards it depends on the type of works you will do. But if you are on a low budget and want splendid performance MSI RS480M2-IL is the best !! I have been using it for 6 months. Excellent performance, no heating, superb graphics(thanx to its Radeon X200 chipset), and good processing. If you can spend a little more go for the nForce 4 Chipset, but remember that every other MBD will need a Video Card to be usable.
AMD Athlon 64 is a fast procesor comparable to Intel's 3GHZ and gives better processing because of its Integrated memory controller unlike Intel which has this on Northbridge. It has Enhanced Virus Protection with XP SP2. AND most important, it does not heat up in summer like all INTEL procs. do.
Thanks ! Hope you buy a nice PC.
Further questions can be asked to
digital_das