Full Text Index with docx and xlsx is not working

Hi,

I am Having a sql server 2012.In My DB, I have one table. In this table, having one colum Document and its datatype is

Image data type. I have created a fulltextindex on this table.If i searching a word in .doc, it will give a result.But if i search a word in .docx,It wont give any result.Why it is not working?Please give me a good installation.

Regards,

Dileep