Desktop Standby not working right?

Unless you know the model of the motherboard and look up the manual to see what options are available, the only way you'll know is to go into BIOS Setup and have a look. It probably wouldn't even be possible to tell you based on the motherboard manufacturer because they may not have the same settings available on all their motherboards; I have ONE Dell computer that I can't force to stay powered off after a blackout and we have had about 4 different Dell models so as you see, standardisation isn't complete.