I would try a system restore first before a complete reinstall.
Use the oldest date before the problem came up.
The only advice I can offer about reformatting, if everything
worked before, then it should work after reformatting and
installing XP. Maybe that guy that did that had some kind
of hardware problem? Maybe he only reinstalled and did
not format?
As to whether you should do the reinstall, if you are tired
of searching for some kind of repair, then do it. I had an
obscure javascript problem. I checked my javascript at
various sites and it passed with flying colors. But a
script I had would not work. Took me all last week,
several hours. Finally found the registry entry that I
needed. So, I fully know the frustration of trying to solve
these problems.
You could hold out a bit, maybe someone will post a
cure.
I am sure if you took your computer to a shop, they would
reinstall. Good luck.