Xml to Xml

Hello i want to converse an xml doc to an other one but leaving out some 
elements, ive tried several ways but it just wont work,
here's what the original xml looks like
<?xml version="1.0"?>
<Bitstream xml:base="../CONTENT/final.yuv" 
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"; xmlns="YUV" 
xmlns:yuv="YUV" xsi:schemaLocation="YUV 
file:/D:/school/DIA-BSDL-1%5B1%5D.1/DELIVERY_2003_08_13/BSDLSource/../CONTENT/SCHEMAS/YUV.xsd">
        <Frame>
                <Y>
                        <Ysample>0 811008</Ysample>
                </Y>
                <V>
                        <Vsample>811008 405504</Vsample>
                </V>
                <U>
                        <Usample>1216512 405504</Usample>
                </U>
        </Frame>
        <Frame>
                <Y>
                        <Ysample>1622016 811008</Ysample>
                </Y>
                <V>
                        <Vsample>2433024 405504</Vsample>
                </V>
                <U>
                        <Usample>2838528 405504</Usample>
                </U>
        </Frame>
</Bitstream>

now i want the same but withouth the V and U elements and their children 
thus something like
<Bitstream ...>
 <Frame>
    <Y>   <Ysample>...</Ysample></Y>
 </Frame>
 ...
</Bitstream>

thanks in advance,
Chris

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