Go here: www.cpuid.org
Download: PC Wizard 2006
Run: PC Wizard 2006 -> Under 'Hardware' on the left click the processor icon
-> Under 'Item' in the main window click processor
-> Scroll down 'Information' to 'Mainboard Upgradeability'
There it will list the socket type and max speed of your mobo. If you buy a new CPU, it HAS to be the same socket type and within the speed listed. Also, check through the PC Wizard to see if your mobo supports Hyper-Threading and other jazz.
If you specify your mobo someone might use something similar