All P4-based CPU's report that they are hyperthreading capable; only certain ones actually have hyperthreading enabled and you can't do anything to unlock it. Only P4 "C" and "E" chips and the single 3.06 "B" chip were able to use hyperthreading. All others are capable but are completely disabled from Intel.
If you're using SDRAM, overclocking your processor really isn't going to release any huge newfound speed boost. Your computer is SORELY needing DDR memory; even without dual channel, a single stick of PC3200 memory would be around 8-12x faster than your current ram.
Most SDRAM benches out at about ~150mb/sec. A stick of PC3200 DDR ram benches out usually around ~1800mb/sec. You get the idea... You're much better off buying a DDR motherboard and at least one stick of DDR ram than crippling your system by keeping your old slow SDRAM.