Yes it is, not really sure if it will fix your problem. But when you install windows updates and other software, the windows installer is used to do this. So you can easily reinstall it by going to the windows update page and it will recognize you either don't have the latest version of windows installer or you don't have it at all.
Go to add/remove programs and uninstall it. Restart your computer then go to windows update and see if that help.
You may (not sure if you can b/c i haven't install SP3) have to roll back your SP3 install, and reinstall it.