Did you have a previous install? It looks like it is registered but somehow you don't have the ability to replace it.

If you're comfortable with using regedit.exe, you could try renaming SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\{9d1b786e-0fd4-4386-abc1-4b920ab32da9} (probably under HKEY_CURRENT_USER, but running as admin all the time can make installers choose HKEY_LOCAL_MACHINE instead). Renaming will get it out of the way so you can try installing again, but you can bring it back if something else breaks.

If you're not comfortable, let me know and I'll make a Powershell script for you can that do it.