Ok I have this same problem only using Poser 9.  If I try to install in default, it wont allow it.  My C Drive is like only 1 GB left in space.  Why I have the D Drive for software.  My C Drive is just for windows.  How do you make this work if you can't install Poser to default and make Victoria 4.2 work?  Really irritating me that if I have to install it to default and I cant do to low space on HD.