Generally, no. You shouldn't remove any of the .Net Framework versions,
these are library files (support files and routines) for programs on
your computer. If a program was written to use version 2.0 it needs
that particular version to work properly, it won't run with version 1 or
3. So that is why I say 'generally' no, if you have no programs written
for version 2 it won't hurt anything but you don't have a readily
available way of determining if you have any such programs so it is best
to not remove these different .net versions. By the same token there is
no need to accept .Net Framework updates, supposing that a version 4
comes out and that you have no programs written to use this version, you
don't need to install it, your other programs will not use it. If you
try to install a program written to use a version that you do not have
you will be prompted to install it or the program's install package will
contain the necessary version and automatically install it.
John