I tried to install that into the same directory where of course everything else is
I'm not sure what your process was here, or what the coded installation process was for the Proteus Pack. I have that expansion pack installer here somewhere, and I'll try looking into that. 32 vs. 64 bit
may be the problem.
Support said something about a sample pool and this and that
The Sample Pool folder is the location where DP looks to first before scanning the the other multisample folders. It's a neat trick for loading samples on a temporary basis. I wouldn't call it good housekeeping for a permanent installation.
But, NO! when I hit F5 there is no magic.
The following process will work, but assumes that all of your .prog files are in a place where they can be 'read'. If necessary, enable hidden file viewing for your system. Search for the program.lst files. Locate the one for Dimension Pro, and delete it. (Careful: There's a programs.lst file for many Cakewalk synths.) It will be regenerated the next time that you open the DP Browser.
The programs.lst file contains what you'll see listed in the Browser. This process forces a 'hard' rescan.