Plug-in Paths (Windows)

Generally, you can set up any customized folder to be a path in Windows. However, these are the most commonly used plugin paths for Windows. 

VST2

C:/Program Files/VstPlugins
C:/Program Files/Steinberg/VstPlugins
C:/Program Files/Common Files/Steinberg/VST2
C:/Program Files(x86)/VstPlugins
C:/Program Files(x86)/Steinberg/VstPlugins
C:/Program Files (x86)/Common Files/Steinberg/VST2

VST3

C:/Program Files/Common Files/VST3
C:/Program Files (x86)/Common Files/VST3

RTAS

C:/Program Files/Common Files/Digidesign/DAE/Plug-Ins
C:/Program Files/Digidesign/DAE/Plug-Ins 

AAX

C:/Program Files/Common Files/Avid/Audio/Plug-Ins 

Settings and Resources Folder

C:/Program Data/Eiosis