De-escaping markup

Hi

I have a bit of a problem in that a system out of my control is producing 
"markup" looking like the following:

<CONTENT>
        This is &lt;b&gt;bold&lt;/b&gt;
</CONTENT>

i.e., with all the perfectly good markup escaped. 

I was wondering if anyone knows of a stylesheet which will convert text 
nodes like this into proper markup, for a whole document.  The above would 
come out like:

<CONTENT>
        This is <b>bold</b>
</CONTENT>

Ideally it would operate on nested tags, as the system (which will remain 
nameless) is also breaking my <table>s.

Thanks for any help.
Cheers,
Ben.