Installing any reader (Adobe, Foxit, Nitro, whichever you prefer) should remake it.
This isn't an answer, of course, to your "why is it missing" question. It's only an answer to your not (yet) asked question "how do I get it back".
Kees
Hey all - I can't find this anywhere else on the web, so here goes. Trying to get normal file-type icons back, I'm in the
My Computer >Tools >Folder Options > File Types tab. That's where the list of ALL extensions & file types is supposed to show up for you to pick the icon & default opener.
This list is notably missing the PDF file extension. It has a ton of other (useless) Adobe acrobat extensions, including .PDFXML, but not the .PDF file type. So I can't do anything to change options for that type.
This is completely batty as I hate the PDF zoo already, but I need to use them for work daily. Can ANYONE help?
* Running WinXP [Pro, 5.1, service pack 3 if it matters]

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic