While there are tomes on the web about recovering XP's speed and more, I fear that these are too much work for most folk.

Over the 9 years you learned to backup to avoid a full wipe out so why not go back to a backup that worked then? Otherwise you can restore it to new, then unless there's some hardware issue it will work just like new.

-> Remember. Speeding up XP is a done some million times discussion. As those don't work for you I think the nuclear option is best.
Bob