You can use
void QSettings::setPath ( Format format, Scope scope, const QString & path )
to set the format (as specified in the doc)
QSettings::NativeFormat 0 Store the
settings using the most appropriate
storage format for the platform. On
Windows, this means the system
registry; on Mac OS X, this means the
CFPreferences API; on Unix, this means
textual configuration files in INI
format.
QSettings::IniFormat 1 Store the
settings in INI files.
QSettings::InvalidFormat
the scope:
QSettings::UserScope 0 Store settings
in a location specific to the current
user (e.g., in the user's home
directory).
QSettings::SystemScope 1 Store
settings in a global location, so that
all users on the same machine access
the same set of settings.
So if you are on Windows and want to write User-specific settings, you would use the IniFormat and the UserScope values and specify the path where you want to write your settings in the path variable.
Hope this helps.