I previously described a set of steps in this blog post that can be used to manually remove the .NET Framework and reinstall it if you receive an error message stating that setup is unable to find the file tmpXXXX.tmp when attempting to install a .NET Framework service pack or hotfix. However, I've heard from a couple of customers over the past few weeks who still received errors related to tmpXXXX.tmp after performing the cleanup steps in that blog post. As a result, I posted a more complete set of steps that you can use to clean up your system and reinstall the .NET Framework. You can find them at http://blogs.msdn.com/b/astebner/archive/2008/03/07/8108332.aspx.
<update date="3/20/2009"> Fixed broken link to the .NET Framework cleanup tool. </update>
<update date="5/6/2011"> Removing the old instructions in this post and pointing to updated steps. </update>