Menu Extension sections in <a href="ms-its:salamand.chm::/hh/salamand/plugins_using.htm">Using Plugins</a>
for a description of basic work with file system plugins and menu extensions.</p>


<h3>Principles and Limitations</h3>

<p>Each file on a disk is stored in short blocks called <a href="ms-its:salamand.chm::/hh/salamand/glossary_c.htm">
clusters</a>. After a file is deleted, its clusters are only marked as free: the actual
data are left on the disk until the clusters are used again for a different file