Xen Windows GplPv/Building
(This is just a cut&paste from the BUILDING.txt file in the source tree)
1. Download and install the Windows Driver Framework SDK (6001 is all that is supported now) from Microsoft. You have to jump through a few hoops to get it, but it is free (as in beer of course. Microsoft don't do the 'as in speech' variety of free). It's also huge. http://www.microsoft.com/whdc/driver/wdf/default.mspx is a good place to start. http://www.microsoft.com/whdc/DevTools/WDK/WDKpkg.mspx is probably a better place to start.
2. Download and install the Nullsoft Installer from http://nsis.sourceforge.net/
3. Use Mercurial (get it from http://www.selenic.com/mercurial/wiki/index.cgi/BinaryPackages) to get the latest sources from http://xenbits.xensource.com/ext/win-pvdrivers.hg.
4. From the top directory, type 'makedist', which will build the drivers for all architectures. If the build fails, then you probably don't have exactly the 6001.17121 that i'm using. Edit set_ddk_path.bat and do a 'makedist' again.
5. Assuming all went well, your drivers should be in target/<os>/<arch> directory. (<os> is winxp, winnet and winlh, arch is i386 and amd64). "Xen PV Drivers <version>.exe" should also be created which is the nsis installer.
See the INSTALLING.txt file for information on how to install.