The Windows PV Drivers are built by a Jenkins server when new patches are pushed into the repo. Build output can be found at xenbits.xen.org/pvdrivers/win/ or through the links below.

To install a driver on your target system, unpack the tarball, then navigate to either the x86 or x64 subdirectory (whichever is appropriate), and execute the copy of dpinst.exe you find there with Administrator privilege. More information can be found here.