After installing DOPUS and answering YES to re-open and then trying to delete the install file fails.
It says the file is still being used (by DOPUS). This seems a recent problem.
I have to shut down DOPUS and re-open once more to do the delete.
Wait about 30 seconds then try again. It's not Opus using it, it's just that the installer stays running for a while waiting to do some clean-up work even though the installer window has closed.
If it does stay locked longer than that, it's probably antivirus or something else locking the file.