Error while installing NS2.34

I thing you are just trying to download ns2 from sourceforge.net (you are actually not installing it from the browser).
Just to solve this download problem, use a better browser like Firefox or Opera.

Further, even after successful download, you can not install ns2 directly on windows. You will need cygwin environment (a unix like environment for windows).

Most of the (Old) versions of cygwin can not be installed on windows vista and windows 7.

So install cygwin on windows xp only.

There may be driver problems while installing windows xp on latest laptops ( and desktops too)