System.Windows.Forms.Application.StartupPath Not working in WPF

Question

i have one window application developed in VS 2005 which is running successfully on client side,My question is that now i want to convert this window application in WPF browser based application, so what should i keep in mind to convert this application to wpf applicaton,
One more thing that in Window Application i have used one mdb file which contain database login detail, so on application startup this file is accessed using System.Windows.Forms.Application.StartupPath+@"/filename.mdb", now im just want to test only whether can i login to my application using WPF or not this time it give me this error "Request for the permission of type 'System.Security.Permissions.RegistryPermission, mscorlib, Version=2.0.0.0, Culture=neutral" (hope some one understand my question)

So if any one who understand my question than please show me some way to develop my application on WPF