Word icon missing/won't launch from start menu or all programs

Suddenly, I cannot open Microsoft Word from the icon pinned to the start menu. When I click it, the start menu collapses but the program does not open. When I looked for it on the "all programs" menu, it is still there but the icon has been replaced by that icon for an unrecognized file type. Word will not launch from there either. I can open Word by clicking on a document (the icons for the documents - and the one on the start menu - are still there). I also went into program files/microsoft office and was able to open Word by clicking on Winword.exe.

Does anyone know why the icon has disappeared from "all programs" and why it won't run from either of the menu links? The other office programs open up and their icons are in place. The only big change I've made to Windows is that I installed IE7. It didn't work on my computer when it first came out so I uninstalled it and used Firefox. I heard that it had much improved and I thought I'd try it again (I like Firefox but the Netflix movie viewer only runs from IE and IE7 does have tabbed browsing but if this is the source of the problem or any other problems, I might just stick to Firefox and IE6 for the Netflix viewing).

I have XP with Service Pack 3. I have already run that xp exe fix registry file and it hasn't made a difference (it hasn't seemed to harm anything on my computer either, thankfully).