If anyone is still looking into this, I've changed one file on my system to resolve this:
/opt/zenoss/ZenPacks/ZenPacks.zenoss.WindowsMonitor-1.0.8-py2.7.egg/Zenpacks/zenoss/WindowsMonitor/modeler/plugins/zenoss/wmi/SoftwareMap.py
(phew!)
Replace Win32_Product with Win32reg_AddRemovePrograms in three lines.
This works for v4.2.4 of Zenoss Core - had it working in 4.2.3, but the newer version of windowsmonitor zapped it out and I just repeated the fix today.