Hi,

Since I upgraded to Sonar 8.5.2 from Sonar I I cannot load Pentagon I anymore.

I get::

Failed to insert soft synth.
The synth may not be properly installed.

I have read related posts about the issue and found that running Sonar as an administrator solves the problem.
However I don't think it is a good practice.

So how to load Pentagon I without running Sonar as an administrator?

Not sure about the "run as administrator" part...I have my UAC disabled and Pentagon loads fine on my system...Perhaps you really do have a faulty installation...

I did have Sonar 8 install and it worked fine. Then I upgraded to Sonar 8.5 and everything works right expect for Pentagon.
I tried to reinstall Pentagon from the Sonar 8 CD since I didn't find Pentagon listed when running the Sonar 8.5 installer.

I had the same problem in Producer 8.5.3 64 bit on Vista Ultimate x64, and also didn't like the "Run as Administrator" option.  So I took off my "musician" hat and put on my "software engineer" hat, spent some time debugging the problem, and came up with a solution.
 
Turns out there is a registry key that the Pentagon DLL is trying to open with full (ie: read/write) access, however the key permissions are set to read-only for non-admin access, thus the insert failure when not running as Administrator.
 
Here's the key:
 
HKEY_LOCAL_MACHINE\Software\rgc:audio software\DXi\Pentagon I
 
Using the registry editor, I modified the permissions on that key, granting the Users group full control, and now I can insert Pentagon I without running as administrator.
 
Standard disclaimers... regedit.exe is dangerous, you can mess up your system, make sure you have a backup, don't blame me if you break something, no guarantee this will solve your problem... etc.
 

I Know this thread is old, but this permissions edit worked for me with Pentagon I on Sonar X2 as well. Thanks for the fix!

Thanks mahotz, I can confirm that the same fix has just worked for me too upgrading from basic Sonar X3 to Sonar X3 Studio. 
 
Receder