Below is the link to the quickspecs for your PC. The supported processors can be found on page 6.
http://whp-cpq.extweb.hp.com/cpq-pro...12703_emea.pdf
No E84xx processors are supported. No processor with a 1333 MHz FSB is supported.
The E84xx processors all have 1333 MHz FSB's, and the chipset your PC has can only take a processor with a max FSB of 1066 Mhz.