I ran office xp on my desktop and 2000 on my laptop until I got to college and _needed_ to upgrade so I could do work with others. Block it with the firewall and you're good. Now I mostly use WordPad, and use a recent (but rarely updated) version of open office on the rare occasions I actually need an office suite or spreadsheet.

If you're worried about vulnerabilities in older software these days, Windows has built-in security features that can help with that, from the sandbox to controlled folders access (intended for ransomware protection, I believe; I use it to prevent my media server from modifying tags)