In my experience, with modern versions of windows, support is a wash for technical users.

I used a windows 2k3/2k8 machine every day for 3.5 years at the same company developing software, and never had a support issue with it. On the other hand, I solely use Macs at home (and, since leaving the aforementioned job to work on my own company), and have also never had a support issue.

However, my grandmother has recently gotten ahold of a vista laptop and a MacBook laptop. She has really shown a greater affinity to the Mac.

Here at HP we're using our own equipment on a fairly large installed base so we actually have a reasonably good feel for relatie support costs.

Also, we have an internally supported and externally available standard Linux environment (LinuxCOE) which engineers (like myself), who run multiple OSes in their cube, can use.

Speaking for myself only here, I would say that the alternatives are available but we can't really ignore what the market demands.

Windows is also a "bargain" when it comes to IT costs. Windows has an excellent track record of strong enterprise support, whereas I have heard from an IT dept that there are all sorts of headaches (and compatibility-breaking changes) to Mac operating systems.

IT departments are also notoriously afraid of what they don’t already know.

Care to explain why a huge swath of corporate IT departments are still running XP and IE6 (or 7) then?

Oddly enough, HP is the one of the major vendors that most appears to be actually planning an alternative to windows. They've already said they plan on bringing WebOS to PCs.