When you run the sage payroll installer on a pc that already has or had a previous version installed you will hit the dialogue picker which invites you to choose which installation you wish to update. This might be what you require – if not then there is no obvious method to force a ‘fresh’ installation ignoring whatever happened before, and you might even have a dialogue asking you to choose from an empty [unpopulated] list – you are unable to proceed.
After uninstalling the application and then deleting the program folders etc attempting to by-pass this problem the really critical tip is to look in ‘C:\Windows’.
If there is a ‘Payroll.ini’ file rename/delete it or move it somewhere else if you are cautious.
Obviously take care and back-up data and/or the system if you are working on a live installation.