I did a little reasearch and found this. I hope it helps
http://h30499.www3.hp.com/t5/Business-PCs-Deskpro-EVO/D530-cmt-sata-problem/m-p/1155475
Your bus speed of the Mobo will determine what is the fastest CPU that can be used. Example 800 mhz or 1333 mhz, and I believe the list for your processors for your mobo is this
Intel Celeron 420 processor (1.60 GHz, 512 KB L2 cache, 800 MHz FSB)
Intel Celeron 430 processor (1.80 GHz, 512 KB L2 cache, 800 MHz FSB)
Intel Celeron 440 processor (2.00 GHz, 512 KB L2 cache, 800 MHz FSB)
Intel Celeron Dual-Core E1200 processor (1.60 GHz, 512 LB L2 cache, 800 MHz FSB)
Intel Pentium Dual-Core E2160 processor (1.80 GHz, 1 MB L2 cache, 800 MHz FSB)
Intel Pentium Dual-Core E2180 processor (2.00 GHz, 1 MB L2 cache, 800 MHz FSB)
Intel Pentium Dual-Core E2200 processor (2.20 GHz, 1 MB L2 cache, 800 MHz FSB)
Intel Core2 Duo E4400 processor (2.00 GHz, 2 MB L2 cache, 800 MHz FSB)
Intel Core2 Duo E4500 processor (2.20 GHz, 2 MB L2 cache, 800 MHz FSB)
Intel Core2 Duo E4600 processor (2.40 GHz, 2 MB L2 cache, 800 MHz FSB)
Intel Core2 Duo E6550 processor (2.33 GHz, 4 MB L2 cache, 1333 MHz FSB)
Intel Core2 Duo E6750 processor (2.66 GHz, 4 MB L2 cache, 1333 MHz FSB)
Intel Core2 Duo E6850 processor (3.00 GHz, 4 MB L2 cache, 1333 MHz FSB)
Intel Core2 Duo E8200 processor (2.66 GHz, 6 MB L2 cache, 1333 MHz FSB)
Intel Core2 Duo E8300 processor (2.83 GHz, 6 MB L2 cache, 1333 MHz FSB)
Intel Core2 Duo E8400 processor (3.00 GHz, 6 MB L2 cache, 1333 MHz FSB)
Intel Core2 Duo E8500 processor (3.16 GHz, 6 MB L2 cache, 1333 MHz FSB)
Intel Core2 Quad Q6600 processor (2.40 GHz, 8 MB L2 cache, 1066 MHz FSB)
Intel Core2 Quad Q6700 processor (2.66 GHz, 8 MB L2 cache, 1066 MHz FSB)
Intel Core2 Quad Q9300 processor (2.50 GHz, 6 MB L2 cache, 1333 MHz FSB)
Intel Core2 Quad Q9450 processor (2.66 GHz, 12 MB L2 cache, 1333 MHz FSB)
Intel Core2 Quad Q9550 processor (2.83 GHz, 12 MB L2 cache, 1333 MHz FSB)
Tho not all of these may work, It gets you started in the right direction. The cpu inserted sets the bus speed automatically if it is one that the Mobo will handle
If you open it up and get the model number off of your motherboard I can do some "Better" reasearch on it and give you a more refined list of cpu's and the socket type. this is what I cam up with based off of the make and model of the computer tho