if u r working on vs 2005 and so on u can find those 
options also

there is no much difference between c# and vb.

Yes, you can managed dotnet framework 1.1 and 2.0 in one
system.  the configuration will be changed on iis server.

Step 1: Go to run prompt   inetmgr
Step 2: right click on your application [Default website]
Step 3: go to properties select asp.net menu.
Step 4: Select asp.net version either what you want.
Step 5: ok.

even your application will not run 

do this steps: in command prompt

cd C:\WINDOWS\Microsoft.NET\Framework\v2.0.50727

aspnet_regiis -i

then try to execute your program.

Thanks
buddy

1) As said in your question it appears to be that u have 
been configuring the application for different versions to 
the same port.
2) We can configure the same application for different 
versions in the same IIS server but need to assign 
different prot number to the application.
3) First of all create a virtual directory for the first 
application tab properties a default home directory appears 
with default port number configure the application and then 
create another application for the another port and 
configure the applcation it work

Note: Type the url with port number to get the application

we can use drill down.This drill down method is use to one 
or more reports use with in report