The Pentium has what you could term a built in co-processor to perform the heavier math functions as well as a larger cache memory built into the chip itself. Also the Pentium has the built in functions which the programs can activate which will heighten performance...speed up...the funtionality. The Celeron is the "value' processor and to be quite honest with you it isn't even worth considering anymore as the Pentium 4 Processors are now very affordable. Also I don't even think Dell uses the Celeron in anything anymore...I believe all is Pentium 4 now. Hope this helps.

There are 3 Generations of Celeron.

The most Recent Celeron 3's are just the same as the Pentium4 down to the socket 478 mounting. The only major difference is the cache which is smaller.

The core corresponds pretty much to the Pentium 4 Willamette,
which has been available since the introduction of socket 423.

100 MHz quad-pumped Front Side Bus (= 400 MHz), providing 3.2 GB/s
High clock speeds (1.7 GHz, faster versions to follow)
1.75 V core voltage
Socket mPGA478
128 KB full speed L2 cache
Instruction Trace Cache
Rapid Execution Engine
SSE2-Instruction Engine


The release of faster Celerons like the new 2.8 GHz version was only a matter of time. On the one hand, the Celeron Willamette cannot compete with the predecessor Tualatin at the same clock speed; that's why it strongly needs higher frequency to justify its existence. On the other hand, the Willamette core with its 0.18 µm is able to run at least 2.8 GHz

The transition from Socket 370 to Socket 478 does not only entail better performance, but also reduces system costs considerably by virtue of raising production quantities for motherboards and chipsets. Basic motherboards with e.g. Intel's 845/865/875 chipsets or SIS 645DX can be used both for the Pentium 4
and the Celeron.

I also don't see any Hyperthreading celerons so if Dualcpu
performance is your Aim then there are low cost Pentium4's in
a very similar price range.

Basically the Higer speed celerons selling at under $99 are to
keep amd and their Duron's at bay.

BTW, Dell still sells Celeron-based PCs.