How might two memory modules with equal specs differ? In any ways that matter? This is a matter of curiosity, as I've already made the purchase.

I bought my daughter a laptop (Dell Latitude E5400) for Christmas, and I wanted to give her at least 3 Gb RAM. Dell wanted $110 to go from 2 Gb to 4Gb, way too much, so I opted to pay $10 to get the 2 Gb on 1 stick instead of 2.

I looked for a second 2 Gb module using Dell's memory specs, Crucial's website, and Kingston's. The specs are: 200-pin SODIMM, 2048 Mb, DDR2-800 (PC2-6400), Unbuffered, Non-ECC, 1.8V, CAS Latency 6 (CL=6), 256 Meg x 64 chips.

I should be able to use any memory module that meets those specs, right? NewEgg shows a Kingston and a Crucial with those exact specs, and when I look these up on the Kingston & Crucial sites, they show lots of compatible laptops but no Dells. When I look up the Dell E5400 on either Crucial or Kingston to find their recommended memory, then look up that memory for compatible systems, they show only Dells.

What's going on here? Do Kingston & Crucial have identical memory modules with different part numbers for different markets? Or is there some other factor, not expressed in the specifications listed above, that would affect compatability?

As mentioned before, this is for curiosity sake only. The Crucial (with the website's compatability guarantee) was the same price as NewEgg, so I ordered it. This is not the always the case (I researched memory for my T61 in the same way, found very different prices).