Can anyone tell me what is the best part of windows 7 & why I buy it ?
Please also suggest me the price of License version.

Thanks in advance ....

If you're currently using XP, then upgrading to Win7 is a good option. The programs in XP runs just as smoothly with Win7. It also comes with excellent driver support. I personally like the over-all GUI. You can change wallpapers every now and then, and even customize it to whatever you like. And the taskbar is somewhat similar to XP’s quick launch but better. I like that it mixes the open and commonly used applications. Another thing that I like about the new taskbar is that once you hover your mouse into it will show a group preview of the windows that are open by that app.