How do you settle on a notebook supplier for your Company?

I’m curious about this. How does a company come to settle on a specific brand or specification of laptop – or any PC for that matter?

Lately, I’ve gone for Dells, as they make it nice and easy. I can call or email my account manager, give him a base unit reference from their website, ask for a number of changes (“I want a spare power adapter, an x res screen and a y size HD instead”) and they do it all for me, and, more often than not, get me a quote within an hour.

So far, I’ve found it hard to find that flexibility and convenience. Unless I’m missing something/someone…

So the question is…

Everyone: What brand machines does your current company use?

IT Pros: Which brand(s) do you buy for your company PCs, and more importantly, why?