In order to build ASIO support into Pd on Windows, you need to download the ASIO sources from Steinberg directly. Their license does not let us redistribute their source files. - Download the ASIO SDK http://www.steinberg.net/en/company/3rd_party_developer.html You have to agree to Steinberg's license, then submit an email address, then they'll send you the download URL in an email. - Uncompress asiosdk2.2.zip into pd/asio