Thank you gregrocker, I think problem solved. but not as I expected. seems like most of them having some kind of driver issues after installation and did some more search on effects after installing Windows 7 on a mac. seems like apple hardware doesn't like windows kernel much as many have reported that some of their software not working or not working because of drive problems.
I asked this because of my girlfriend. she loves the beauty of mac but for the OSX not so much. so asked me that whether is it possible to install windows and have its maximum capacity. but seems like it caould be achieved, but if something goes wrong, she wont be able to correct it just by running repair installation of windows dvd. so I dropped the idea and will suggest some thin notebooks from samsung and lenovo. thank you very much for the help. repped.