Hi.
You can add it by yourself in the xboxmediacenter.xml.
CODE
<files>
<bookmark>
<name>X Drive</name>
<path>X:\</path>
</bookmark>
<bookmark>
<name>Y Drive</name>
<path>Y:\</path>
</bookmark>
<bookmark>
<name>Z Drive</name>
<path>Z:\</path>
</bookmark>
...
You know that you should not save any data on this drives?