I have a plugin - Arturia Spark - which will not show up in my list of VSTs in Sonar X3 Producer on Windows 8.1. I have the correct folders being scanned etc - other VSTs in the same folder show up fine.
After some research, i discovered that "Spark.dll" is missing a "short name"  - this is a windows thing - if you want to read more about it go here:

My problem is I already have short names turned on. The VST in question is already short enough Windows does not generate a short name for it. Apparently X3 still relies on this file name format to generate it's CLSIDs. So for me - no Spark.
I tried renaming the dll to generate a short name - but that crashes Sonar (and Live). I assume that's because its breaking whatever copy protection scheme Arturia has.
So I'm currently stuck. Anyone else experience this issue and/or know a workaround or fix? Does the latest generation of Sonar fix this issue by not relying on short names?
 

UPDATE: I was able to resolve this by:
- See above post about renaming the dll to generate the shortname (aka "DosName").
- Run plugin manager to get the "broken and renamed" spark dll - I used "Spark 2.dll"
- Close Sonar.
- Rename the dll back to Spark.dll
- Open Regedit (yup - registry hacking time!)
- Go to "HKEY_CURRENT_USER\Software\Cakewalk Music Software\SONAR Producer\Cakewalk VST X64\Inventory"
- You will see all your VST plugins listed under here. Find your "Spark 2.dll" entry and select it.
- In the details for this key, you will see many entries. Update the following:
DosName: from SPARK2~1 to just  SPARK
FullName: from Spark 2 to just Spark
FullPath: from [your vst path]\Spark 2.dll to [your vst path]\Spark.dll
- Close regedit and open Sonar - let it or make it do a scan of your VSTs.
- Spark now appears in list of VSTs, in plugin manager, and now I am able to use it in my sessions.
 
Still don't know why this happens. I also have another machine with similar setup, and it shows up fine there. But at least I have a fix. If you try this, please KNOW WHAT YOU'RE DOING when editing the registry. You can really mess things up here if you screw it up.