To Develop a silverlight Application we need the following requirements.
1. Microsoft Visual Studio .Net (Latest Version is VS 2010)
2. Silverlight SDK kit
3.Experssion Blend .(Which is used to Design graphics,Animation etc through Experssion Blend in silverlight)
4. Operating system which support all the above
Note: Windows xp, windows vista,windows server ,MAC will support to develop the silverlight application.