Step1:- Go To root folder than

app/etc/local.xml 

open local.xml file and change below "CDATA[admin]" code.

<admin>
<routers>
<adminhtml>
<args>
<frontName><![CDATA[admin]]></frontName>
</args>
</adminhtml>
</routers>
</admin>

NOTE:- use only small character.

Step2:- go to var/ folder and delete cache folder.  Now open admin with you're new admin name url..

by