Question : Problem: Confused about 20 vs 24 pin MB and powers supplies

I have a new Biostar MB with a 24 pin power supply hook up yet my power supply has only a 20 pin connector.  I have a seperate 4 pin plug for intel so what would plug into the odd 4 of the 24 from my MB.
I want to get a 500 watt power supply and they all advertise 20/24. Do they still malke a 24 pin atx power supply

Answer : Problem: Confused about 20 vs 24 pin MB and powers supplies

what is the motherboard model.
The 20/24 spec means that there is a 20 pin main connector with the extra 4pin to make up a 24 pin connector. The 4 pin is a breakaway piece that allows it to be used or not depending if the motherboard has a 20 or 24 pin connector. The 20 pin PSU with 4 pin you mention on the old PSU cannot be used on the new motherboard power connector in the way you describe, "into the odd 4 of the 24 from my MB".
The extra 4pins on the new motherboard are for the added power that the  PCI-e slots on the motherboard will require for video cards. There is the possibility that the old 20 pin PSU will work if no high end video card is installed, but that would depend on the +12v Amperage rating on it, and how much is needed on the new motherboard.
Look on thesticker of the old PSU and there should be ratings for each power rail. The +12v amps are important here, and there may be more than one +12v rail spec. Please post those specs here.