This typically happens when trying to run a fresh install on an environment that has had CISPro installed on it, but was then "uninstalled." Typically, the installer log will have an entry that says something like this:

Configuring IIS
Error while setting up the IIS App
There is is already an app named, /cispro, on the site, Default Web SiteC:\cispro\deployarea. Please give a different name.
Reverting server to previous state.

SOLUTION: Even if you've deleted the app from IIS, it's possible a "phantom" app still exists in the app pool. The phantom apps must be deleted:

1. Navigate to "C:\windows\system32\inetsrv\config"
2. Make a copy of "applicationHost.config" (just in case you screw something up)
3. Copy the file "applicationHost.config" and paste it to a folder where you can edit it (e.g. your documents folder)
4. Edit the copied file and look for the "sites" block. Remove entries that should not exist, for example:

5. Copy the modified "applicationHost.config" file back into "C:\windows\system32\inetsrv\config" and overwrite the existing one

6. Reset IIS

To check for phantom apps:

1. Open IIS
2. Select "Application Pools"
3. Right click an application pool you suspect may have a phantom CISPro and select "View Applications"
   1. Click "Remove Filter" to see all apps for all application pool
4. If you see any apps that you've deleted from existing IIS sites you've got a phantom app!

NOTE: It's possible that, even if the main CISPro WebApp application was removed successfully, the sub applications (Inventory/Ng) may still exist as phantom apps, and those may NOT exist in the applicationHost.config for removal.  To remove these sub-phantom apps, you will need to manually add the main application back in IIS, then manually remove the sub applications, then main applications.