So I asked Microsoft if there's any possible way that there are that many different types of computer components out there floating around and actually supported by Vista.
My lowly machine has only about 90. Of course, I don't have but one hard drive and one of most other things, so that's a hugely limiting factor. Still, even Microsoft acknowledges that 2.2 million is a lot of printers, CD drives, and USB keys. "That number does seem huge," Michael Kingsley, a Microsoft senior product manager for Windows, told me.
The 2.2 million number refers to the number of unique plug-and-play hardware IDs out there. If that's still gibberish, which it was to me at first, then let me explain. Almost every different type, make, and model of hardware that exists has its own unique hardware ID. That means that if you buy an 80-Gbyte Seagate DiamondMax D540X-4D model number 4D060H3 and I have an 80-Gbyte Seagate DiamondMax D540X-4D model number 4D080H4 -- ever-so-slightly different versions of the same product -- our hard drives would likely have different hardware IDs in Microsoft parlance. However, if you were behind me in line at Best Buy purchasing the exact same HP printer as I did (you copycat), then our hard drives would almost certainly have the same ID.
That said, a huge number of these IDs, Keigley said, are storage devices. He estimated there are hundreds of thousands of hardware IDs for hard drives alone. Checking out Seagate's site in order to get those model numbers, I see that Seagate has, in its current line-up, 27 pages of products with something like 50 products per page. That's more than 1,000 products -- and potentially unique hardware IDs -- in Seagate's current line-up alone. Seagate's but one storage vendor in a sea, and those are only the products Seagate sells today, not those it's sold before.