It is quite a new and frequently updated application.
I have posted on the developers website with no reply yet. However there is a similar post suggesting temporarily disabling anti-virus software and using some utilities to unlock and then delete the folders after which the software can be reinstalled.
If the installer doesn't contain InvokeAsAdministrator in the code it will not cause the UAC prompt to execute which in turn will not allow the installer to gain elevated rights and you will get Access is denied.
In other words right click the installer and select 'Run As Administrator'
It is quite a new and frequently updated application.
I have posted on the developers website with no reply yet. However there is a similar post suggesting temporarily disabling anti-virus software and using some utilities to unlock and then delete the folders after which the software can be reinstalled.