Changing tag text

Hello all,
I need some guidance on how to go about changing a tag name in a
transform from one XML file to another XML file, or actually appending
something on the tag name like so:
<Atag>some data</Atag>
to
<xsl:Atag>somedata</xsl:Atag>

I need it to add the "xsl:" to each tag. Seems like it would be a
simple answer but just not seeing it right now and any help will be
greatly appreciated!

Thanks,
Hank