Bill D is right, I think, about the "new and improved" Open Office being Libre Office. I haven't looked at it seriously, but reviews have been good.

What I don't understand is why System Restore keeps telling me it can't do its job.

Failure of System Restore to fix something, if you went back a month, most likely just means that whatever corruption is causing the problem was there a month ago, and was saved in the restore point made then. Sometimes it appears that Microsoft programs will "work through" a minor corruption until it's recognized, but then will point it out to you and crash the program forever after until it's fixed.

The "Repair" method in Control Panel, if you find it, should work if the installation files (.CAB) and installation logs are still on your computer. They nearly all are in the original setup, but can be deleted by Disk Cleanup if you check them for removal. Back when Hard Drives were tiny little things, some people removed them to make space, but more recent (even WinXP era) machines generally have enough space that they're not noticed.

If the .CAB files are gone, you'd probably have to have an installation disk to reinstall.

An unlikely possibility is that even though the program is "unsupported" Microsoft update might still install critical security patches and occasionally one of these, or a botched install of one, can corrupt a program. At Microsoft update (on the web) it should be easy to look at "recent updates" and some of them can be uninstalled if there's good evidence they've scrod (past-perfect subjunctive tense of screwed?) you. If that's a possibility, you should look at Microsoft for removal instructions for the specific patch you think needs to be killed.

John