My right click response in Win7 Explorer became intollerably slow. I install so much junk all the time that I had no idea what may have caused it. Nirsoft to the rescue with ShellExView. The problem may be a Context Menu add on from some third party, even Microsoft. The first one I disabled was Windows Live ID Sign-in Helper. Disabling it seemed to do the trick. Sign-in Helper must have been installed when I installed some of the Windows Live Essentials.
Some of the key Nirsoft utilities are available in the Liberkey Ultimate download.