Search for files with a specific file extension in Windows 7 [duplicate]

In Windows Explorer, I would like to search for all files in a specific folder and its subfolders with the file extension .doc. To do that, I tried to enter .doc in the search bar on the top right of the window. That gave me as a result all the files containing doc, not necessarily with that file extension, including folders named "doc".

In Windows XP, there was if I remember correctly something to only search for one file type, but I can't find anything like that in Windows 7.

How to only search for files with a specific file extension and not other files which contain that extension in their name?