How to remove OpManager Service

I am trying to install OpManager. I previously was using the free version. I ran the uninstall from the Control Panel. Now when I go to re-install OpManager I get a message saying 'do you want to uninstall opmanager?'. I reply yes, then get a message telling me that the OpManager service is being removed. The process runs to completion. I then try to run the installer again, and get a message asking me if I would like to remove Opmanager. I then get a message saying the service is being removed. And on it goes. I have checked the registry, control panel and file system, and can't understand why the OpManager installer thinks the OpManager service is running when it isn't - it isn't even in the list of services to start in the registry.

My boss is dead set on buying Argent - I can't see the point in spending 10000 dollars on it when this product will do the job just as well. I thought if I demonstrated OpManager to her she would prefer that over the Argent.....but if I can't get the demonstration to work, well......looks like it's Argent for us.

Can someone tell me how to manually remove OpManager?

My email address is gerry.locke-at-greatlakes.nsw.gov.au. Any suggestions would be greatly appreciated.