Installing .net framework 2.0 service pack1

Hi,
can any help me in installing .net framework 2.0 service pack 1 from NSIS

thanks in advance

1) Check if any version of the .net framework is installed first
2) Tell the user the required version is not installed
3) Install it by either downloading it from the main site or if you included it with your installed then extract and install

thanks for your reply
i have the NSIS Script which installs .net framework 2.0 by checking whether it is installed or not.but i am not sure of doing that for service pack 1

if any one has done that already ... please give the snippet of code which does the trick