That will depend on what programs you have installed and which .NET Framework version each requires.
Unfortunately there is no easy way to tell. You would have to contact the publisher of each program you have installed and ask them what (if any) .NET Framework version their software needs.
Bottom line: remove .NET Frameworks at your own risk. If you remove a framework, any programs you have that need it will refuse to run.
Is there some reason you want to remove .NET Framework 1.1?
It doesn't take up much disc space, and uses no resources at all until called to support a program that needs it.
