sending form parameters as URI Segments

[eluser]Sanjabs[/eluser]
I have a form code (simplified for use):
<form name="search-institution" action="<?=base_url()?>institutions/index" method="get">
Search Text :
<input type="text" size="15" maxlength="100" name='keys'/>
<input type="submit" value="Search" name='Search2' />
</form>


When i submit the form: the uri looks like:
www.sampleweb.com/institutions/index?keys=value
but i prefer it to be like
www.sampleweb.com/institutions/index/value

I have disabled $config['enable_query_strings'] as FALSE;

But still query strings are not diabled???

Solutions please?