How can you tell what?
The version of windows if new will most likely be 64 bit, this is easy to find out in control panel/ system.
Your version of Sonar? well you installed it, so did you choose 32 or 64 bit?
On windows 7 64 bit Below the desktop icon will say- Sonar 8.5 (64bit)
I am not sure if that would show if I installed the 32 bit version in W7, but I would assume it would.
On my windows XP 32 bit laptop it doesn't have the (32bit) in the text below the icon.