Depends on the model # of your HP ... IIRC, they did put Dual-Channel support in their "High-End" models, which your P4 3.06 would qualify as. 🙂
Post a model number here so we can dig up the specs.
But anyhow, if I were you, I'd keep the RAM out. It's CL3, and whatever you've got in there is probably CL2.5. Performance gains would be negligable at best.
- M4H