But what motherboard you've got? You didn't tell me your make and model. Is it ASUS? GIGABYTE? What model?
If that is HP DC7600 then that is the list of compatible processors:
* Intel P4 521 (2.8/800/1M) processor with EM64T
* Intel P4 531 (3.0/800/1M) processor with EM64T
* Intel P4 541 (3.2/800/1M) processor with EM64T
* Intel P4 630 (3.0/800/2M) processor with HyperThreading
* Intel P4 640 (3.2/800/2M) processor with HyperThreading
* Intel P4 650 (3.4/800/2M) processor with HyperThreading
* Intel PD 820 (2.8x2/800/2xMB L2 Cache) Dual Core Processor (not available on the USDT)
* Intel PD 830 (3.0 Ghz clock speed, 800 MHz FSB, 2x1M L2 cache)
* Intel PD 840 (3.2 Ghz clock speed, 800 MHz FSB, 2x1M L2 cache
* Intel Pentium 4 660 (3.6/800/2M) processor with HyperThreading
* Intel Pentium 4 670 (3.8/800/2M) processor with HyperThreading
Celeron Processors
* Intel Celeron D Processor 331
* Intel Celeron D Processor 336