I just had a problem with a Windows XP user. somehow the default to open .pdf files was changed. so I was simply going to go to folder options and go to the file types then change pdf to reader.
but for the user, the buttons were greyed out, and notepad was selected as the program to open pdf's.
So I thought it was a permissions thing, so I logged in as my account, and sure enough, the buttons were NOT greyed out, but under my profile, reader was the default for pdf's. so I guess it's according to the profile, how default programs are chosen.
so my question is, is there a way to globally for ALL profiles, choose the default program to open a file?