I recently acquired a shiny new free plug in.  I had trouble getting Sonar to find it, and now my plugin situation is totally screwed.  Every time I do a new scan, Sonar comes back with a different set of plugins!  Sometimes there are VST3s, and sometimes not.  Sometimes it finds my Izotope plugs, sometimes it doesn't.  I've reset the VSTs several times now, and I can't seem to get everything back.  As I've been looking through the program files for the scan paths I need to set, I'm totally befuddled.  There are .dll files all over the place!  Each vendor creates it's own folder, but puts it's .dll files in multiple locations.  Even when I think I've set the scan paths right, sometimes the plugs don't get picked up.
 
I don't know that I've asked a very good question here, but if anyone could offer advice on getting a plugin situation fixed, I'd love to hear it.
 
Seth

Try a reset and rescan. 

Most installs I have seen provide a default installation path for plugins, and allow it to be changed by the user, during the installation process script.
 
I usually put all 64-bit plugins into the C:\Program Files\Cakewalk\Vstplugins folder, and every VST3 install I have done has deliberately placed the plugins into C:\Program Files\Common Files\VST3 folder.
 
I DO have some plugins in C:\Program Files\Common Files\VST2 for some reason, and I allowed some Steinberg stuff to go into its default plugin folder of C:\Program Files\Steinberg\VstPlugins.
 
And lots of freeware that doesn't have any installation script, but is just a dll or a small folder with a dll and some other components - all of those kinds of plugins I download to My Downloads into a Plugins folder, and then I manually copy those into the C:\Program Files\Cakewalk\Vstplugins folder.
 
I also do still maintain a small folder for 32-bit plugins that I wish to have loadable in my 64-bit Sonar sessions, and I put those into a sub-folder within C:\Program Files (x86)\Cakewalk\Vstplugins called Bridged (I use JBridge, but would do it this way even if just using the Sonar-included BitBridge).
 
I do not know of a simple way to consolidate a bunch of plugins that are scattered all over the place, nor do I know why you get different results when doing a Reset and a Full Rescan of all of your plugins.
 
Bob Bone

I'm managing to slowly get things rebuilt now.  I've been adding one folder to the scan path list, scanning, adding one more folder, scanning again, etc.
 
I think part of my problem is that .dll files with the same names are showing up in different folders, and I apparently don't need to have every folder that has a .dll in the scan path list.  I'm finding the whole plug-in management thing to be rather confusing, but I'm slowly getting it worked out.  I'm down to only one of my must-have plug-ins that I can't manage to get Sonar to find.  This is a weird one, though, since I've located it in the folder system and other plug-ins in the same folder have been successfully loaded.

You can get the same .DLL name in different folders because of different versions. You could have a VST2, VST3, 32 bit and 64 bit versions in different folders with the same name. Hope that helps.