MakeShift
So I slept on this. I got up this morning and located the Vst scan file in the Shared Utilities folder. I moved this file to a safe location and copied in the old Vst scan file from X2. X3 now appears to be doing a complete scan of all Vst's. I will check out the program here in another 20 min after it has completed.

I have the exact same issue with my Vista system.  Where did you get the *old* X2 VST scanner executable?  I only have one shared folder so I'm guessing my X3 install overwrote anything there from my previous Sonar installs (I have everything from 8.5 through X3 still on this machine).
 
I tried reinstalling X2 but the VST scanner executable remained the X3 version (I could tell by the date)...odd.
 
 

Bill,
 
I had backed up my system before doing the install.  So, I just went into the old files and grabbed it.  Yes, it appears to over write the old VST Scan file.  This allowed me to scan any VST's that were already on my system, but none of the new ones that come with X3.  However, Addictive Drums, since it is a separate down load, with its own serial number, scanned fine with the X2 VST Scan file.  That leads me to believe that the new X3 VST Scan file has something in it that acts as a handshake to allow the new plug ins, instruments, VST3 and ARA to work in X3.
 
I filed a bug report at the request of Noel and Seth above, but have not heard anything back as of yet.  I am guessing that it is lower on their list of priorities compared to some of the other issues they have been dealing with.  I felt it was really pretty great for Cakewalk to even offer to look into the issue with Vista, when Vista is not officially supported.  I am guessing that it might be something fairly simple to figure out and fix, however.  
 
I continue to run X3 without any issues other than no ARA with Melodyne and none of the Nomadic plug ins.  I will eventually upgrade to either W7 or W8.  I have a few songs that I am finishing on this rig and then have to find a time when the family goes away for a couple of days and lets me work on the upgrade.

Thanks, Mike.  I am avoiding the Windows upgrade to preserve my old Emu 1820M.  I will just cross my fingers and hope they fix the code in an upcoming patch.

any update on this
 
 
when sonar tries to scan it stops and I get this error
 
            k32 EnumProcessors could not be located in dynamic link library Kernel32.dll

I haven't heard any more news on this.

Tech support told me the official answer to this issue is to upgrade to Windows 7 or 8. vstscan.exe does not run in earlier operating systems.

That answer is not quite acceptable.
While I can understand X3 not being supported in Vista, the X3 upgrade also rendered the VST scanner unusable in previous versions installed on my Vista computer.
I installed X3Studio a couple days ago, and ran into the same error message as you guys. The I found this thread.
Bummer, or so I thought.
I looked at what Mike had tried, and it seemed like he was on the right track.
Remember, computers are very stupid, literal machines. They can be tricked, if you do it right.
So I dug up an old programming trick.
From Windows Explorer, go into Program Files>Cakewalk>Shared Utilities and rename VSTscan to something else. I used "broken_VSTscan".
This prevents the system from recognizing that VSTscan exists. This is the key.
Now install an older version of Sonar that does run properly under Vista. I used SHS6 because I had the disc handy.
Do a custom install, and install only the program files. there is no need to re-install all of the plugins.
The installer will install an unmollested earlier version of VSTscan.
The install routine will not overwrite a newer version with an older one, but it will install the older version if there is a void where it should be.
Now, not only does the VST scanner work in X3, the X3 plugins are available to my older versions.
I realize we will ultimately have to move to W8, but in the meantime, I hope this is helpful to others using Vista.

It looks like X3c has fixed this issue with Vista.  Thanks Noel, Seth and Bill for fixing this issue and showing incredible customer support.  I am guessing there are still quite a few folks, like formally me, that were hanging on to Vista because I didn't want to mess with something that had always worked great.  Some one using Vista will have to let me know how it works.  
 
Funny enough, last weekend I installed a new 2T HD and installed Win8 Pro 64.  I am busy reloading all my VST's and hope to finish them up this weekend.  Lesson learned, always keep all of your program Reg Keys and Licenses somewhere in one easy to look up location.  I have spent the majority of my time tracking Reg Keys and getting the VST's up and running.  Using and test driving the new clean install of both Windows 8 and X3, as a base program, it is running better than it ever has.  My CPU usage has dropped incredibly.  Even the CPU fan is quieter and hardly come on with this new set up.  I am anxious to really dive into this new configure and push some limits, but I want to get everything installed again before I do. 
 
Of the VST's I have reloaded so far, they all run smoother as well.  EZ Drummer, Addictive Drums, Amplitube, and S-Gear....smooth.  Steven Slate Drums 4 seems to be the only one having issues at the moment.  I have a service request into SSD and am working on that one.
 
I held off on installing the X3b upgrade, anticipating that X3c would be out any day now.  This weekend I will update to X3c.
 
Again, thanks Cakewalk for incredible support.