I need to know if the installer is running in 'Repair' mode (when the user goes to the Add/Remove applet in the Control Panel, selects my app, clicks 'Change' and then selects 'Repair MyApp..'.)

Is there anyway I can obtain whether or not the installer in running in Repair mode from inside my CustomActions DLL code?

Bump. Anyone?

If you're re-running a custom action because of a repair, the case-sensitive Installed property will be set because the product is already installed. A condition of Not Installed should stop your custom action running again during repair. The other property that's set IIRC is REINSTALL so a condition of Not REINSTALL should also work.