One question...have you tried to install SP2 right after
a clean install of XP. Many problems with SP2 are
fixed with a fresh install of XP then immediately install SP2
(before internet access).
You can also create an XP cd with SP2 already
on it (slipstreamed) very easily with a free software
called autostreamer. This saves a bunch of time
when installing SP2 and actually creates exactly
the same cd that comes with now SP2 already on it.
Hope this helps.
Dave