Mobile Phones, at the early stage of their development were used for making calls allowing user to be mobile but didn’t typically support applications, multitasking and may not provide complete file system like today’s mobile phones support applications like games applications, maps, music players, social network and many more applications. Now the question arises why it is so important to have your applications developed for mobiles? They are important if you are including your business processes. An airline application is a good example of this. You can reserve and purchase tickets, check in, get alerts etc. Since the public in large is the user of your application, it should be made available on all major mobile platforms. To simplify development, developers initially run, debug and test their applications in a software version of the phone also known as an emulator. This enables the creation of your application in a standard, familiar environment and can be deployed onto a phone when ready to use. Windows mobile/ phone 7 platform has an integrated development environment which provides tools like visual studio 2010 express, XNA game studio 4.0, windows phone emulator, Microsoft expression blend for windows phone and platforms as silverlight .NET framework 4.0 to allow a developer to write, test and deploy applications into the target platform environment. Microsoft offers these IDE and SDKs for free to the developers. You can download them from internet and install on your computer. Windows phone developers tools only run on windows Vista sp2 & later. Developing application for Windows phone can be achieved by using two approaches. One is developing Data Driven applications using Silverlight and another is Mobile Graphical Game applications using XNA. Any person with prior knowledge of .NET can easily develop applications for windows phone because the GUI in the framework is user friendly and tool bars available in it.