Also, Sonar sometimes (if the plugin is written properly) only shows the 64 bit version if both are installed.
In the plugin manager view the centre window pane shows the plugins while the left windo selects the type, like DX, VST3 etc. If Sonar is showing both plugins you can exclude one of them. Select VST or VSTi if an instrument and when you click on those plugins one at a time, you'll see the path at the bottom of the plugin manager window and that should tell you whether it's the 32 or 64 bit.
Select Exclude plugin at the bottom left of the left window. It in no way effects that plugin except in Sonar it is no longer visible in any menus.