Lost Stand-by power function

I reinstalled WINXP in same dir because of flaky startup. WindowsTask manager has tab for shutdown and the stand by function is now “Greyed out” only Hibernate and remaining functions below it are usable. Hibernate takes a LONG time to finish but now doesn’t shgut off computer Only leaves message “OK to shut off your machine.” Device manager shows computer as “standard PC”. Should be ACPI compliant. Have abit BH-6 mb and power controls were working as documented. Now things don’t work right anymore with power!
Any help appreciated,
MontyW