I have a d530CMT with the following configuration
CPU: Pentium IV HT CPU 3,2 GHz/1M/800 (Prescott)
Heatsink: Scythe Samurai with a Delta AFB0912VHE fan
RAM: 4x1 GB PC3200 KTH-d530/1G RAM modules
GFX: Radeon HD3850 AGP
S-ATA DVD-RW
120 GB S-ATA SSD with XP Pro
HP Z400 475W power supply (the stock PSU is too weak)
I also tried the 3,4 GHz Prescott but unfortunately there is no microcode update.
You really need to replace the stock heatsink cause it's unable to keep the Prescott cool (even those Northwood chips can get pretty hot).
I hope this helps a bit