Another silly question

I have another question, sorry, but I see a few categories that don't seem to have corresponding badges. I see a Vista and XP category, but when I expand the list of possible badges when in profile view, there are no corresponding badges for those categories. And there are a couple of blank spots in the assembled badges layout in this view. Is it just me or is it just that there aren't badges for those categories?
 
Solution
Badges are assigned to tags, not categories.

AFAIK there are no XP/Vista badges, probably because they're becoming increasingly uncommon and the new forum software with badges was added pretty recently.
Ok. I guess since there are Windows 7, Windows 8 and CPU categories, and corresponding badges, I just assumed that was how it worked. Most of the other categories seem to have corresponding badges as well, with a couple of exceptions. Anyhow, thanks for clearing that up on the XP and Vista badges. So if you answer questions in those categories, do you just not earn any points towards a badge or does it go towards some other area?
 
Categories have nothing to do with badges, except for some slight correlation. For example, there is no Networking badge but there is a LAN badge and an Internet Access badge.

Answers count towards nothing but a counter. Solutions get credit towards each linked badge, plus the general counter for number of Solutions, which has a couple of badges attached.