XML problem with special characters

hi,
i try save/load a XML with special characters like this:
ão ção ólá
when i save nothing goes wrong but when i try open using internet explorer
or any software they result in a error in that characters.
the header that i using is this: <?xml version="1.0" encoding="UTF-8"?>
<dataroot xmlns:od="urn:schemas-microsoft-com:officedata" generated="2010-03-07T12:33:07">

what i need change for correct the problem?
thanks a lot for your help :)

http://www.w3schools.com/XML/xml_encoding.asp