This happens sometimes with Windows XP installations. Unless the display drivers are installed, power saving actions such as standby and hibernate are not supported.
Whether the system supports hibernate can be checked - http://pinvoke.net/default.aspx/powrprof/IsPwrHibernateAllowed.html
Is there something similar for checking standby support?
check out all the porwer management functions here
there is IsPwrSuspendAllowed which u could use it