I am planning to assemble CPU.. Already have 500GB hard drive and 2GB ram..
May I know other hardware needed and some points to consider in choosing motherboard and other things needed..

The biggest question is what do you plan to do with it?

If you're building a desktop rig for basic usage, I'd recommend just assembling basic parts with a good value. If you're building a gaming rig, it becomes a bit more complex.

I personally always build systems with standalone graphics cards because I want the option to play games. I personally also like to go with a bit more than 2gb RAM...usually more like 8gb RAM.

The motherboard you purchase will be dictated by the RAM you have. What type of RAM is that?

If you aren't technically astute and haven't built a system before, then either buy a pre-built one with the features you want, or find a local white-box builder (computer store) to build one to your specs. I have built a lot of systems (and am certified by IBM and others to do so - factory trained and certified computer technician by IBM, Apple, Compaq (now HP), AT&T, and Zenith), but my current workstation I had a local builder do it to my exact specifications. That was 8 years ago - the price was very competitive, and it still works fine - I'm writing this on it right now. 8 cores, 8GB RAM, many terabytes of disc, and good audio (built-in) and video (nVidia card) w/ Bose speakers and dual 24" HD displays (1920x1200). The builder burnt everything in and tested it extensively before delivery. If there was a problem, he would have dealt with it before bothering me.

I only had to write him a check, and plug it in!

zomgmike DDR... What should i consider in choosing motherboard? Any brand or type can you recommend. My apologies for frequent questions.. Thanks.