Assuming you mean .Net assistant and use Firefox as a browser (pronounced at dotnet) have a look at http://www.dedoimedo.com/computers/ms-dotnet-firefox.html
How do I get rid of the Net Assistant program that keeps popping up every time I click on Facebook now? The removal instructions they give don't work. Net Assistant does not appear when I try Add/Delete. Neither does the word Zero. The removal tool link does not work. I downloaded a removal tool called Perfect Uninstaller and Net Assistant does not appear on its list, Thanks.