The XP2200+ is really a bad overclocker. Most of those CPU's are one of the earlier Thoroughbred A cores and it's really hard to get them running even a little faster.
I recently tried to overclock a 2200+ from week 44 (Tbred A core). As the CPU was MP locked, I tried to raise the FSB (Nforce 2 board, so no problem in raising the 133Mhz FSB there ).. I couldn't even get it stabilised over 145Mhz FSB (no temperature or powerissues!).. really too bad.