another processor upgrade question.?

upgrading to that processor will barely show any noticeable difference. The best way to increase your performance is to add more ram.

the p4 2.8GHz is the slowest P4... at least that they're making now, it features an 800mhz front side bus which would make it process faster than the celeron which has a 533 mhz FSB... but if you have a celeron processor, it's very likely that your motherboard doesnt support the faster FSB... so the p4 wont work to full potential like the celeron will

the clock speed of the Celeron is higher, but the lack of extra cache on the CPU will actually make it slower; the Pentium 4 will turn out faster but not toooo much :) just enough

Noticeable in benchmarks but hardly in actual applications. If you are planning to spend for an old P4, better consider the cheap new Celerons:

http://www.xbitlabs.com/articles/cpu/display/conro...

It gets spectacular when overclocked.

http://www.xbitlabs.com/articles/cpu/display/conro...

There are now plenty of cheap LGA775 motherboards capable of 1333mHz fsb. That should give you a wide upgrade option in the future.

Will your motherboard help the better FSB? additionally, does your memory run at 800Mhz, if no longer then you would be constrained via the cost of the RAM. i could nevertheless ought to assert that the overall performance advance would be minimum.

I won't notice the difference, if you want to see that your money was well spent go for a dual core cpu.