Would Intel(R) Celeron(R) CPU 2.80GHz fit into IP4 socket ?
Celeron or Celeron D? Is the Pentium 4 Socket 423 or Socket 478 or LGA 775?
Celerons at this clockspeed should fit Socket 478.
Celeron Ds at this clockspeed should fit LGA 775. (It's possible there's a 2.8GHz Celeron D that fits Socket 478 but I'm not so sure on that.)
You should really check the processor compatibility list for the motherboard in question though...just because it fits is no guarantee it will work!