HP locks out all the overclocking stuff, dude.You'd need a new p35/p45/x38/x48 motherboard to properly overclock your chip.
You could download Setfsb and try to find your pll and get about 200 more Mhz..That's about it.
PS:the main setfsb site is down..use the tom's one;It works.
It looks like they don't OC very far...this is #1 for that chip
http://valid.canardpc.com/show_oc.php?id=2308118
Did I mention you need a p35/p45/x38/x48 motherboard to properly overclock it?
Expect 3.4-3.8 on air/water
I'd sell it and get a new setup..should be able to get around $100 for it