Add full text index facility to SQL Server instance
When you install a clustered instance, the fulltext components are installed by default and it is not possible to de-select them. If you don't have fulltext installed, you're in big trouble. Are you sure the components are not there? What does SELECT SERVERPROPERTY('IsFulltextInstalled') return? If it returns false, I'm afraid you will have to reinstall this instance. I had the same thing happening to me once and there was no way other than reinstalling from scratch.