Once i have updated to microsoft. net framework 3.0 can i delete 2.0 version?

I would not recomend it I beleive 2 and 3 work together and 3 requires 2. So try it if you want, but you might have to reinstall 2 and 3 if it causes problems.

Once i have updated to microsoft. net framework 3.0 can i delete 2.0 version?windows media player

Unlike java and flash which should be removed, I believe you still need the previous versions of .NET (1.0 /1.1 / 2.0 / 3.0).

You can try uninstalling it if you want at your own risk, but I'd keep it.

Once i have updated to microsoft. net framework 3.0 can i delete 2.0 version?windows live messenger internet explorer

no... they are seperate and offer different functionality..