This question cannot be answered well with the original author missing.  What can be answered is why you would develop on Windows in 2008 (as apposed to Minix, SCO, Linux, GNU Hurd?). 

Windows has and had:
* The best market penetration.   To get more users of an application you can write it on Windows
* Wide range of development tools and software for development.

Rather than use Microsoft only frameworks, it takes some effort to use portable libraries and frameworks.  These days, Android is the new Windows.