You're probably seeing this error because The SolarWinds Network Performance Monitor service is still running. You might try going into the SolarWinds Orion>Advanced Features>Orion Service Manager, clicking Shutdown Everything, and then attempting to run the Install again.
If you're using VMWare, make a snapshot before attempting upgrades. I've learned that the hard way. :)
I have tried making sure everything is stopped first and I still get the error. Also I have tried renaming the file to verify it is not in use and it let me do that.
I am doing this on a image of the production server so I don't have have any pain if everything goes sideways. Just want to iron this out before trying to upgrade Prod.