[libvirt] virtio-win-0.1-22 balloon install fails on 2008R2

Trying to install the virtio-win-0.1-22.iso balloon driver on Windows 2008R2: E:\Wlh\amd64>x:\microsoft\WinDDK\7600.16385.win7_wdk.100208-1538\tools\devcon\amd64\devcon.exe install BALLOON.inf PCI\VEN_1AF4&DEV_1002&SUBSYS_00051AF4&REV_00 Device node created. Install is complete when drivers are installed... Updating drivers for PCI\VEN_1AF4 from E:\Wlh\amd64\BALLOON.inf. devcon.exe failed. 'DEV_1002' is not recognized as an internal or external command, operable program or batch file. 'SUBSYS_00051AF4' is not recognized as an internal or external command, operable program or batch file. 'REV_00' is not recognized as an internal or external command, operable program or batch file. Any help appreciated. sean