you havent specified the board you have. if you bought the system in Celeron PPGA 366 days, it probabely will support only PPGA, maybe a BIOS update will let you use an FCPGA processor. if your motherboard does not support FSBs over 100 MHz then all you could get is 100 MHz FSB P-III 850! Celeron has just reached 1 GHz and is still at 100 MHz FSB.
you could use a Powerleap adapter to use FCPGA processors on you board if needed.
<font color=red>No system is fool-proof. Fools are Ingenious!</font color=red>