In a recent MarkLogic upgrade on Windows Server 2008 the following issue was encountered:
The uninstall of the previous version successfully completed. The upgrade installer was initiated and it went thorugh the install process. At the very end it posted a message 'Rolling Back Action' and promprly reversed the installation.
The issue was caused by the inital uninstall not removing the MarkLogic service. Check this in the task manager services panel. If the MArkLogic service is there then run the command line with the following command:
sc delete MarkLogic
If this fails to remove the service but returns a message along the lines of 'this has been marked for deletion', then reboot the machine and the service should get removed. The installation can then be run successfully