Several months ago I posted about getting the grandparent's computer up to date because for whatever reason it wouldn't do it the Windows Update way. Went down today with the update on a flash drive, ran it, and discovered that the reason it wasn't updating wasn't the slow internet.
It was because the update found Trend Micro Internet Security 2008, knew it wasn't compatible and wanted it removed manually. (Apparently the Windows Update way of installing the update doesn't bother to let the user know about trivialities such as this).
Curiously, Trend Micro has never been installed on this computer, and even if it was, 2008 would definitely not be compatible with Windows 10. So I figured that it may have been something in the registry bought over via Windows Easy Transfer from his old Windows 7 box which was in turn Easy Transferred from his old XP install that setup had found and was truly upset by.
After consulting Google, it turns out that during the install, the installer spits out an XML file which lists the problem files. Actually really helpful once you know it exists (I cannot remember the exact name, but it's in the C:\
$WINDOWS.~BT\Sources\Panther\ folder, and is an XML file that starts with some gibberish and ends with Human Readable). So looked at it, and found what the offending Trend Micro 2008 file was.
Apparently, one of the folders from the original XP Easy Transfer to Windows 7 was that of the Trend Micro 2008 installer that was sitting on the desktop, and setup had found the main Trend Micro 2008 executable in it. It then made the assumption that, because the executable exists, Trend Micro 2008 therefore must be installed.
So, simple fix: nuke the folder. Did that, and everything went off without a hitch. No obvious problems or complaints, and he's now able to compute in peace without it nagging him to update to a new version of Windows (for a few months at least). Hopefully I won't need to do it manually next time.