At these times, you can go to the Registry and manually delete the entries. When you do this, it will appear to Windows as if the application is not installed. Then, you will be able to go on with your business. So, where do you delete these entries?

You first need to go to the General Information view, Product Properties, and find the Product GUID property. If you wish, you can copy this GUID to the clipboard (minus the curly braces), then run Regedit, and search for it. But searching takes a while.  So, in the registry, you can go to the following place and look for the GUID that matches your installation project.

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall

When you find this node, you can start your search for the Product GUID there.  It will take no time at all, and when you find the node, you can just delete it.  Then the next time you run your installation, to Windows and to InstallShield, it will appear as a first-time installation of your product.

Of course, after you delete the entry from the registry, you wll still have to manually delete the product files from your hard drive.  You have to clean up after yourself.