What's this about SSE enabled? You can't disable SSE/SSE2 as far as I know; it's hardware level in the CPU and always used if a program is coded for it. With a dual core, if you installed XP as Multiprocessor PC(which it will, by default, if you did a reinstall when you put in the dual-core), you will see two CPUs in device manager.
And no, you don't really need the drivers if you're not going to use Cool n Quiet.