I've been using Dim Pro 1.5 and Proteus VX with Sonar X1 Essential on a Windows 7 laptop.  The laptop motherboard died.  Had to buy a new one.  Of course, this one has Windows 8.  I've loaded Sonar X1 Essential and it opens just fine.  I haven't tried to play back any of my files because I can't get Dim Pro to install on X1 or libraries from Proteus VX.
 
I downloaded a fresh Dim Pro 1.5.011 from "my account".  It installed just fine on my computer...as a stand alone, but won't show up in X1 VSTi listings no matter what I try.   When it installed as a stand alone, I installed it as 64 bit and it defaulted to the Program/Cakewalk folder.  It's supposed to be in the Program (x86)/Cakewalk and VST folders, but moving it there doesn't change anything...except when you click on Dim Pro.exe it won't run as a stand alone from the Program (x86) location.
 
As for the Proteus VX library, a "blank" icon loads in the Proteus VX (which shows up nicely in the Softsynth area of X1), but all of the libraries are "not a valid .exb file."  They all worked fine on the old computer.
 
Somebody please help.  And thanks to everyone in advance for your responses.  Cakewalk forum members have NEVER failed to provide a solution!

By the way, I don't know if this is useful information, but Dim Pro would not install on my computer using the registration number on the "my account " page of Cakewalk.  I had to right click on the icon and then "run as administrator" to get it to accept the registration number...which it did immediately.
 
Don't know if that makes any difference loading into X1, but I thought it might be worth mentioning.

You always have to run as administrator to register DimPro.
 
If DimPro is installing in "Program Files" and not "Program Files (x86)" you are installing the 64bit version. It is not clear from the post if you need the 32bit or 64bit version. If you are running 32bit SONAR you need the 32bit version of DimPro. Run the installer and select the 32bit version.
 
As far as the Proteus VX, it probably requires a compatibility mode setting maybe this post will help http://forum.cakewalk.com/FindPost/2272726

When I installed Dim Pro on the Windows 7 laptop, it wasn't necessary to run as administrator.
 
I thought about installing as 32 bit, but I'm not sure about Windows 8.  Windows 7 allowed you to run the laptop as 32 or 64...I've only seen 64 on Windows 8.  However, I will try that because I think you're right about the 32 bit deal.
 
Also, thanks for the link on Proteus.  I will check it out.
 
Thanks for your response.

The installations should be run as administrator regardless of the OS. The installation instructions also indicate that registration must be done as administrator.
 
Whether you install the 32bit, 64bit or both versions of the software is up to you if you are running the 64bit OS. When running a 32bit OS, only the 32bit versions install.
 
On a 64bit OS, running 32bit applications will only be able to address up to 4GB of RAM. Running 64bit applications will be able to address all of the RAM available. When running a 64bit DAW, you should also run the 64bit versions of yours plug-ins if available.