scale down from .net framework 3.5 to 2.0.

Goto WebSite->Start Option->Build and change the target build to .Net Framework 2.0

In this case, if you are using webproject hosted on IIS, then goto webdir and in the properties you need to set it to .Net Framework 2.0

If you don't see .Net Framework 2.0, and you are sure that .Net framework 2.0 is installed on your machine, goto C:\Windows\Microsoft.NET\Framework\v2.0.50727 and run "aspnet_regiis -i" command to register the .Net framewok with IIS.

-Rahul Gade

in project properties you can change the target framework

For my windows application, I did the frame work change.. but I am using a web service, for that also shall I need to do any change.Where is this web directory?

it should have application pool with the relevant framework version

Actually I have published this windows application and trying to run the setup in a system in framework 2.0 is available but my application is still requesting for framework 3.5 SP1 . What should I do for it?
Please do reply.

you must change all the projects to older framework

Can I do the framework change of web service by my windows application only?

If you want to modify the framework requirement of a specific project, you just create another solution and add the other project to other solution. This way you keep both projects (with framewok version 2.0 and 3.5 separate)

2.0 is subset of 3.5, so all app targeted for 2.0 will work on 3.5, while if on any system only 2.0 is installed you will be able to work with app built with the target for 2.0.

-Rahul Gade

Actually sir I have changed the framework requirement by changing the target build as per you said but while running its setup.exe file it is still demanding 3.5 framework. Why is this happening?

You may need to change the WebService Target Framework.
Simply right-click your ws project and choose "Property Pages" (it should be the last context entry).
Then select "Build" on your left and change the framework:
 
Regards.

You might have selected framework 3.5 as pre-requisit while developing your installer project. Could you please verify.
In this, there is a option to either bundle the selected version of framework with installer or download it from microsoft website. If you have selected wrong version here, the installer will keep on expecting to install the said version.

-Rahul

Actually after changing the target build, I have installed the .net framework 2.0 with my application but while installing my application,it download both(my application as well as .net framework 2.0) but later demand for .net framework 3.5.

thanks