HiJack This and Repeated Excel Install

Hello,

I have recently, over the last month or so, been getting a pop up "Windows Preparing to Install" whenever I try to open an Excel document. It's like Excel has to reinstall every time I use it.

Related to this, there is a security update for Excel that never installs, so I'm assuming that's the cause of this repeated installation problem.

I read that I should run HiJack This to find the problem regarding the registry key, but that's like another language to me. I ran HiJack This and am posting the log with the hope that a mod can read it and tell me what's up and what course of action I can take. I notice there are a few "file missing" listings in the log, and not sure what that means either.

Thank you, much appreciated.