DAZ installers for V4 and its addons are very old. There were never updated to comply with Windows Vista, Windows 7 or even PoserPro. Installing V4 into Program Files will bring you a lot of troubles.

I still have my Poser 5 installation. I never use P5 anymore, but I contains my main library and after every Poser update I added the P5 runtime as an external library. It has the big advantage that an old installer finds the P5 runtime and installs it there and I can use it from any version of Poser