Is it possible to take windows off a computer and put Macintosh on it?

You can install Windows on a Mac. You could delete Mac OS X but then you would not have a Mac so it would be rather pointless as you may as well have purchased a Windows computer to start with.

Not entirely true. My long experience has taught me that Mac hardware is generally more reliable, the screens are usually better, and battery life and lifetime of Windows PCs is pathetic compared to the Mac. The only downside is getting used to the different keyboard...