Make sure you have them in the correct folders. Trying to remember (at work now without a copy of Poser), hair goes in runtime/libraries/hair/newfolder, and poses go in runtime/libraries/poses/newfolder. (Newfolder being the specific folder in which you want them organized.)

Make sure that you don't have any sub-folders off of 'newfolder', because they will not be displayed within Poser.

When unzipping files, be careful of the folder to which they are being extracted. Some files are zipped with folder paths that may not match your Poser directory. When I first started with Poser and downloaded free files, I had the problem of not being able to find what I just unzipped, because I wasn't paying attention to the extraction paths. Every now and then I still have to move a file that's been tucked to something strange like:

D:Poser4librariespropsfurnitureProgram FilesMetaCreationsPoserlibrariespropscouchescouch.pp2