Looking to upgrade processor chip need help

I'm looking to upgrade the processor chip and don't know which one to get. This is the information from dell about my computer a dell 4300 with a 1.4 ghz processor.

Microprocessor type Intel® Pentium® 4 microprocessor that runs at 1.50, 1.60, 1.70, 1.80, 1.90, or 2.0 GHz internally and 400 MHz externally
L1 cache 8 KB first-level
L2 cache integrated 256-KB at full microprocessor speed
System Information
System chip set Intel 845
DMA channels four
Interrupt levels 15
System BIOS chip 4 Mb (512 KB)
System clock 400 MHz data rate

 

As fast as I can for the least amount of money. Id like around 3.0ghz maybe faster if the price is not that much if my computer can support the chip.

Also would it be cheaper to get a whole new processor instead of just a chip.

 

If I were to search for these processor's what should I search for, for it to be compatiable with my pc.

 

Why would it not run over 2ghz.

 

2.8 was the fastest 400 MHz FSB socket 478.I belive what ddp was saying was the Dell Bio's may not have been revised to accept anything beyond 2ghz the 2.8 might work but at a reduced speed.No prescott cpu are any 533,800 FSB socket 478 will work.

 

How would I know if the bios can run fast?

 

i would visit the motherboards webpage and under support/downloads or BIOS updates it will give some information on the newer bios updates, including when they were released, and what they "fixed" or allowed the user to do...it might say something about the board supporting a faster processor...if not, then i don't think it would be worth it uprgrade the CPU, but thats just my opinion...let us know how you made out