Question : Problem: How much can I upgrade the processor in my existing motherboard?

My old Dell desktop originally came with a Pentium 4 1.5 GHz processor.  It is a Socket N (478 pin) processor with a 400FSB

3K362      PROCESSOR, 80531, 1.5G, 0, 400FSB, SOCKET N, D0

What I want to know is if I can put a Northwood or Prescott core Pentium 4 chip into this same motherboard?  The Northwood chip I am looking at is the 3.06 GHz Hyperthreaded 478 pin socket, with a 533FSB.  I also am looking at a Prescott 3.0 GHz chip, with extra heatsink and fan due to the extra heat issues associated with the Prescott core.

I know a lot about software, but these "nuts-and-bolts" hardware issues have me sunk.  Any input would be appreciated.

If I need a new motherboard, I may just abandon this machine, unless someone can tell me that a new motherboard is easy to acquire, and install into my existing OEM case.  Maybe that would not be a bad route if it would also allow me to increase the maximum allowable RAM (currently 1 gig).

Thanks!

Answer : Problem: How much can I upgrade the processor in my existing motherboard?

Ok to go into a little detail.
First to  upgrade your existing machine to a much more modern or reliable system hardware and operating system wise.
The machine you have has a 250 watt power supply: This is not very good  for upgrade options.
The motherboard options for upgrade are limited. You have a agp slot only at 4x.
Your ram is  limited also so on and so  on.

Now too go to upgrade  options.
First you mustt relize that dell does not buy motherboards that are not modified for there machines from mobo mfg's.
What this means is that the possibility of buying a new motherboard say from ASUS as a example mfg.
Taking the new motherboard out  and directly placing it into the case. Is a very unlikely scenario.
You may have to drill some new holes into the case to seat the  motherboard properly or make some other form of modification to the case to make it all work.
You will need a new power supply with depending on what other hardware you buy such as motherboards,  ram, sound cards, drives, video card or cards and so on. at a starting point of probably no less then 450 watts. That is  very subject to what parts  you buy though including the processor.
You may very well actually need upwards of over 600 watts.
So as you can see  upgrading your machine is not going to be easy and it is more likely that by the time you are done you will have either bought a new machine or bought the parts for a new machine and assembled it yourself.

Im not trying to turn you off of upgrading what you have but im trying too tell you that your options for upgrades on that dell 4300 is very limited, Usually upgrading dells are more of a pain in the butt as dell  provides very limited upgrade options for the machiens  they  use  outside of adding a drive and so on.
Even the BIOS on most dells are modified to the point they really do not support the original mfg specs they  might limit the possible cpu that  you could install with out changing the BIOS and so on.

Personally i buy no machines from MFG such as dell or gateway compaq HP or anyone else anymore for the afor mentioned reasons. They all do something along the way to limit your options of upgrading without going through them or  buying a new machien from them.
Building a machine isnt really that hard and for the most part it can be cheeper then buying one from a vendor if you choose the right parts. Also your upgrade  options at that point are really very unrestricted.
But to go back to your orignal question.
No you cant use that chip  in that  MOBO.
When replacing a processor
MOBO  Ram and PSU are your main concerns : ARE THEY COMPATABLE? is what you need to ask.