Make sure you are the administrator of your system. 

Also, if I remember correctly, after installing V4, you need to run the .dat file to initialize the figure.

Personally I never install directly into my runtime folders.  I have a folder on my C Drive called "Unzipped" that I install or unzip content into.  After I've looked through the folders and organized and renamed folders as needed, only then to I drag and drop into the runtime folder.

I keep a dummy poser.exe file in that folder. It's simply a text file with the extension changed to .exe.

When installing Daz content, I stop it from searching, and point the path to the unzipped folder on my C Drive.

"It is good to see ourselves as others see us. Try as we may, we are never
able to know ourselves fully as we are, especially the evil side of us.
This we can do only if we are not angry with our critics but will take in good
heart whatever they might have to say." - Ghandi