[wix-users] Upgrading from Visual Studio installer project

[Parkes, Kevin]

I'm replacing a Visual Studio installer project with WiX. The old installer had the "Everyone" / "Just Me" option that Visual Studio adds so in most cases existing installations will be per-user.

As I understand it, a per-machine install (ie my new installer) can't upgrade a pre-user installation, so users will have to manually uninstall the old version before installing the new.

What I'd like to do is have a launch condition in the new installer telling users to uninstall the old version before proceeding. I've added  <Upgrade> and <UpgradeVersion> elements and a <Condition> based on the Property <UpgradeVersion> should set. However, that property isn't getting set and the log file shows:
"FindRelatedProducts: current install is per-machine.  Related install for product XXXX is per-user.  Skipping..."

So, how can I test for an old installation and block the new install if found?

Thanks
Kevin Parkes