[Zope] Plone/Zope URL problem

Dear Sir I used Plone/Zope for manage the doccument for my company. my problem is that every time I request the URL it add the word Plone to my URL http://mywebsite/Plone/Plone/Plone/ How could I sold this problem? when I change the root Plone site ID to another ID it does not work. could you tell me how to change the Plone root site ID? Thank