Hi -- all the Windows builds of plugins linked at
http://vamp-plugins.org/download.html are 32-bit versions, but they will work fine in a 64-bit version of Windows so long as the host is also 32-bit.
(64-bit Windows is happy to run 32-bit binaries, but the host and plugin must match -- in this case both must be 32-bit.)
The installation folders are listed at the bottom of
http://vamp-plugins.org/download.html. Note that on a 64-bit Windows, you must install 32-bit plugins in
C:\Program Files (x86)\Vamp Plugins
or your language's localised equivalent -- with the (x86) suffix -- and not just in Program Files.
Chris