Fixing Outlook Install Error "application with the same identity is already installed."
SOLVE
Go to Control Panel (Windows Start Menu > Control Panel) and search for Uninstall a Program. In here uninstall any instance of “sidekick” or “hubspot sales”.
Remove everything from from the folder at C:\Users\%YOURUSERNAME%\AppData\Roaming\Sidekick. If this folder is not visible you will need to display hidden folder. To do this select “organize” in the top right and then click “folder and search options”. In this new pop-up select “view” and on this page under “hidden files and folders” select “show hidden files and folders” and then click ok.
Go to Registry Editor by typing regedit in the start menu and clicking on regedit.
Click on the triangle next to HKEY_CURRENT_USER to expand it.
Collapse Add-Ins, Outlook, Office so you're back in the Microsoft folder
Expand VSTA, Solutions
Under solutions you will see one or several folders. Click on one and in the right window you will see a bunch of info. One of the rows will say “Product Name"
Go through every folder under solutions and find one where the Product Name is “Sidekick for Outlook"