It will be worth mentioning that every 32-bit (x86) application can run on 64-bit (x64) O.S (considering only a set of 64-bit hardware available).
To run Windows Application (32-bit) developed using ASP.Net 2.0 on Vista 64-bit Operating System, you need to strictly specify the application to run at x86 (32-bit) and NOT All CPU's option. Follow the steps mentioned below to build application for x86 (32-bit) O.S. :
1) Open the application that you want to run on 64-bit O.S in VS 2005.
2) Open Solution Explorer by Pressing Ctrl+Alt+L or by clicking View>Solution Explorer.
3) Select the project, right click on project and than click properties.
4) Select Compile Option and press "Advance Compile Options".
5) Than select Target CPU to x86 and press OK.
6) Rebuild/Recompile the application. Create installer (.msi) file of the application and install on 64-bit O.S.
This will do the trick and you will be able to run a 32-bit (x86) application on 64-bit (x64) O.S.
