The 'upgrade' was probably WMP 7.5 or some lower version, as that is what MS had on it's websites for a while. You over-wrote 8.5, and then removed the whole thing...and then created a backup with no WMP at all.
The only way you'll get WMP back is to hard-reset but NOT reload your apps from backup.
This isn't a bad thing anyway. All your PIM is backed up in Outlook, and important files will still be in synced "My Documents" file. Reloading all the apps from scratch will give you a nice clean registry, better & faster running (hopefully), and probably some more RAM.
I have done hard-resets every 6 months or so to 'clean things up' from trial software and general abuse of the system.
Chris...