Why does Visual Studio (2008 and 2010) put three bytes at the beginning on newly created text and xml files?

Why does Visual Studio (2008 and 2010) put three bytes at the beginning on
newly created text and xml files?

When I create a new TEXT or XML file within Visual Studio (2010) three
bytes are set at the top of the file. They can't be seen unless you're
using a binary editor.

Why are they there and what do they do?
Is there a way to stop Visual Studio from putting them there?
As it stands I cannot use Visual Studio to XML files because these bytes
screw up the parser.