Well I was going to say "Bah! - so what if they're multiplier locked" because you could just run PC3200 memory and have an instant XP3200+, but then I saw your system specs.
Your 1.5gigs of PC2700 probably won't be reach a 200Mhz FSB. So unless you swap that memory for something faster (ahh, get a new mb too!)....Ahh what am I talking about? Your running a T-Bred @ 2.2Ghz now? It seem you are in an interesting situation because I don't know if you would really see a huge difference even running a XP 2500+ right out of the box @ 166FSB?