Well, I don't know what c:\windows\inf\sysoc.inf is used for
If you choose not to archive during Service Pack 1, meaning you can't uninstall it, then it will not be in Add/Remove Programs
I remember the old Win9x TweakUI had a nice tool to remove entries in add/remove without removing the software.
I installed TweakUI for XP
http://www.microsoft.com/windowsxp/p.../powertoys.asp
But it has no such panel. And it seems in TweakUI you can pick which items show in the control panel, but Add/Remove is not one you can toggle off and on.
So after all that, I don't really have a solution for you as of yet.
If your 'user's are just users and not administrators, then at least they can't uninstall any of those hotfixes.
I will have to mess around with the different user groups to see what they can and can't do. I am not sure what users can turn messenger back on in SP1 and not.