hi there, I have developed a windows application using C# VS 2008 and Sql 2005 express, i have testes the application on my machine and it works fine, my machine is win32 bit, when i tried the application on windows 64bit it keeps giving me an error message on the start of the application,although i installed the sql express on that machine but should i install .NETframwork3.5sp1 64 bit also? , the target machine is widows 7 64bit, also is there a technology or a way to make the application work in the following sequence: 1- the CD is auto run 2- the setup checks for the installed prerequists and install any necessery one without the interference of the user. one last question,should i rebuild the application on an 64 bit machine to make it work on 64 bit machine? thankx