Transform XML to XML

I have an XML file that I want to filter out certain elements.
(actually, it's the tracking files for my blog, and there is a lot of
blog spam in them. It will take forever to remove by hand.)  So the
first thing I'm trying to figure out is how can I create an XSL file
that will take as input an XML file and output *exactly the same* XML
file as output?  (The next step will be to start selectively omitting
elements from the output.)

FYI, I'm using XmlWriter as my editor.

I've done a lot of work with XSLT, but every time I start a new project
with a slightly different need I feel like I'm back at square one
because nothing ever seems to work as I expect it to!

Thanks in advance.

-Mike