You probably have changed the operating system locale to a language other than Japanese.
Xbench 2.9 is a non-Unicode application and therefore it needs that the locale for non Unicode program is set to Japanese.
In Windows 7, this is done via Windows Start > Control Panel > Region and Language -> Administrative -> Change System Locale and you need to restart your machine.
An alternative to avoid changing locales and restarting Windows is to use Xbench 3.0, instead which is a Unicode application. There is a 30-day trial for Xbench 3.0. It is 30-days of actual use, not 30 calendar days so the trial might last much longer than 30 days.
Also, if you are using Studio 2014 or Studio 2015, we strongly recommend to use Xbench 3.0 with the Xbench plugin for Studio. This 5-minute video shows how the plugin for Studio works: https://www.youtube.com/watch?v=daWkATVCkvg