Thanks for all the replies.  NI B4 works for me on my win7 64bit.  I just want to find out if it works on Win 10.  Thanks again.  Yes, I do know that Vintage Organs is the "sampled" version of B4, and it is useable, but I still like that relic of B4 from time to time.    
 
I plan on just getting Win 8.1 for the new DAW, and wait several months to see if Win10 is what I need.  At the very least, the death of my motherboard is forcing me to move "forward" from Win 7 to Win 8.
 
Thanks

You don't need to apologize for using B4. I thought it sounded great. I would still be using it if it was 64 bit. And I loved Windows 8. My system was way more stable on 8 than it was on 7. YMMV

B4II and just updated to win 10, tried it standalone,  works for me

Thanks.

Wondering about Pro-53.  I didn't have it installed when I upgraded to Win 10.  Now I'm trying to install and it hangs at the very end of the install process (updating system configuration please wait).  I asked NI support and they told me, incorrectly, that dxi's don't work with Win 10 (I wanted the dxi installed because I was trying to work on a very old project in the days when directixer was how you got VSTs to run in Sonar). Any thoughts on why it stalls in the final stage? 

smoddelm
Wondering about Pro-53.  I didn't have it installed when I upgraded to Win 10.  Now I'm trying to install and it hangs at the very end of the install process (updating system configuration please wait).  I asked NI support and they told me, incorrectly, that dxi's don't work with Win 10 (I wanted the dxi installed because I was trying to work on a very old project in the days when directixer was how you got VSTs to run in Sonar). Any thoughts on why it stalls in the final stage? 

I too would be interested in learning what others have done to get Pro-53 to work in Win10.  I can't answer your question as I have only just last month stepped up to Win8.1, but I do plan on making the big step to Win10 once all the drivers I need are released.  
 
So do report back on what you have figured out regarding Pro-53.

Hi
When I upgraded this week to windows 10 pro 53 would not open In Sonar Pro or FLStudio.
 
I could not uninstall It either as the Unwise uninstaller  kept freezing.
I managed to uninstall Pro 53 with Revouninstaller and It worked a treat.
Now I have the same question .Does anyone know how to get this working In Windows 10.
 
It Is no good asking Native Instruments as they say they are discontinuing Pro 53.
I find this really unacceptable that they do not even try to help.
They just avoid the questions and say some people have managed to run It In Windows 10.
No loyalty there and no suggestion of a cheaper crossgrade to something for our troubles .
Pro 53 cost me best part of £100.
 
I think It Is hard cheese and cut your losses
 
All the best
John

both pro 53 and B4 work fine for me on Win 10 in Sonar Plat.  They load up bit bridged (or j bridged) and have had no issues. I was just messing with Pro 53 the other day.  I freaking love the sound of that synth!

Hi Sven
 
I cannot get to the latest Pro 53  for the life of me.
 
I have the original cd and the original Pro53 works fine no problems.
It Is when I put the update In and then you have to go via Service Centre.
It puts tha damned UNWISE EX UNINSTALLER IN which messes everything up
after loading in the update ,I get a box come up saying there is a failure in the Promap line 1 txt
What that Is ,I do not know as I am not a programmer.
I cannot get Pro 53 off of my drive at this stage as the Unwise exe freezes.
I had to use  a free uninstaller program to uninstall.
I put the Pro 53 disc In again and loaded up to the first version .
It works flawlessly
 
All the best
John

Some other things that don't work in Win10 (I took both Microsoft's and NI's word for this and didn't try them myself): Rig Kontol 2 and Rig Kontrol 3. No problem with Guitar Rig 5, however.