When you say "Content installer" what do you mean?

Are you talking about the several gigs of content that comes with Poser (in a bunch of executables)? If so, the problem probably is, as already mentioned, that you've got your content runtime in Program Files and UAC is getting in the way.

Or are you talking about installing from 3rd party vendors at Renderosity or Daz? A lot of 3rd party content won't install using the Poser interface because the zips aren't set up correctly, so you just need to extract the files and drag them into your content runtime(s) manually so that the folder structure of the "runtime" directory in the zips matches the "runtime" directories in your content.

Daz zips wrap the "runtime" directory in a folder called "content" and this will play havoc with the Poser content installer. It needs zips to have the runtime folder in the root of the zip. If this is what has happened, you may find that you have a content directory that looks like this:

Poser Pro 2014

Runtime

Content>Runtime

If so, you just need to move that second runtime located inside "content" so that it is actually merging with the first runtime.

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PoserPro 2014, PS CS5.5 Ext, Nikon D300. Win 8, i7-4770 @ 3.4 GHz, AMD Radeon 8570, 12 GB RAM.