qcllectiongenerator not generating .qhc file

[NIXIN]

I have a .qhp file like this

<?xml version="1.0"?>
<QtHelpProject version="1.0">
<namespace>HelpMenu</namespace>
<virtualFolder>doc</virtualFolder>
<filterSection>
<toc>
<section title="Exe Help Menu" ref="HelpMenu.html">
<section title="Ellipse" ref="Ellipse.html"></section>
<section title="Rectangle" ref="Rectangle.html"></section>
</section>
</toc>
<keywords>
<keyword name="Insert rectangle" ref="Rectangle.html"/>
<keyword name="Insert ellipse" ref="Ellipse.html"/>
</keywords>
<files>
<file>HelpMenu.html</file>
<file>Rectangle.html</file>
<file>Ellipse.html</file>
</files>
</filterSection>
</QtHelpProject>

and .qhcp file like this:

<?xml version="1.0"?>
<QHelpCollectionProject version="1.0">
<docFiles>
<generate>
<file>
<input>HelpMenu.qhp</input>
<output>HelpMenu.qch</output>
</file>
</generate>
<register>
<file>HelpMenu.qch</file>
</register>
</docFiles>
</QHelpCollectionProject>

and I run

qcollectiongenerator.exe HelpMenu.qhcp -o HelpMenu.qhc

But I am getting only HelpMenu.qch. HelpMenu.qhc file is not generated. Can't understand why?? Please help