Are you referring to a "User Search"?  If so, the search feature within the USERS module allows you to search by any profile field (including COUNTRY) but you'll only get results for fields that have data.  That is, you'll want to REQUIRE the "COUNTRY" field during user registration if you intend to search users by that field.

As for searching by "registration date", you'll have to add your own solution.  This is not too hard using the REPORT module or free third party module like SQLView.  Here's an example of how to easily show the most recent user signups using AdvancedDatagrid:

   http://www.eguanasolutions.com/DNN_Blog/EntryID/2.aspx

...and another showing a similar task using SQLView (which supports sortable results columns as well as querystring paramaters which provide an easy way to add search):

   http://www.eguanasolutions.com/DNN_Blog/EntryID/15.aspx

-mamlin