here's a review of a pentium 4 531 at newegg. It's dated 12/29/2006. Enjoy!
Pros: It works fairly fast, and programs seem pretty snappy. This Prescott has a fairly hefty 1MB L2 Cache and a nice 800Mhz FSB. Paired with a good video card, it could churn out respectable framerates in many games.
Cons: It runs so hot in my case that too much intensive work will shut down the computer. I can't do any gaming with it because it is just that hot. The stock cooling is also really loud and not that effective.
Other Thoughts: I suggest getting a Cedar Mill processor rather than this. They're supposedly a lot cooler, made from a 65nm process, and have an extra MB of Cache.