Happens often enough to be a pita…
firstly try this:
put in your original halion 4 DVD in your hard drive whilst trying the updater (assuming you do have a halion 4 dvd and didn’t upgrade from halion sonic, if that is the case, then try the halion sonic dvd, although not sure if that will work)
if the above doesn’t work, then you have to uninstall halion 4 (not the content, just the app, and plugins via program uninstaller in control panel), and reinstall it then do the update.
it happens often to some of us with halion sonic (hasn’t happened to me with halion yet)
sigh
rsp