If your using Compaq bios they may not support the CPU. You will need to contact Compaq to see if they have bios for that mobo to support the chip. You just ran into one of the many problems in trying to upgarde an OEM machine.
Asus Rampage/Maximus Formula, Q9450@3.73ghz, 4GB OCZ Reaper pc8500,EVGA 8800GT w/EK full cover block, 3 Seagate320s in raid0 and Samsung750gb ,Zonar D2X,Corsair HX1000, Water cooled:Fuzion w/accelerator nozzle ,1 D5/EK top and 1 DDC w/xspc top pumps,(2) MCR320 rads,120mm fans(6),140mm fans (2),Gigabyte Aurora case