<p>How can i stop the host machine entering <code>standby</code> mode while my application is running?</p>

<p>Is there any <code>win32 api</code> call to do this?</p>

This article
http://www.codeguru.com/cpp/w-p/system/messagehandling/article.php/c6907
provides a demo of how to do this from C++ (thought he article is framed as if you want to do it from Java, and provides a Java wrapper).
The actual code in in a zip file at
http://www.codeguru.com/dbfiles/get_file/standbydetectdemo_src.zip?id=6907&lbl=STANDBYDETECTDEMO_SRC_ZIP&ds=20040406
and the C++ part of it is under com/ha/common/windows/standbydetector.
Hopefully it will give you enough of a direction to get started.