Wanted to know if ya can use an older power supply on a ATX MB by changinging the connectors  wanted to swap MB in on older system but wanted to keep the original supply. 

    HAPPY NEW YEAR 2005 

  Yep you can use any power supply you want as long as the voltages you are sending to the MB is the same, On many power supply's you can even adjust the voltage to make sure its at the exact value needed. 
Microwave

hm, a word to the wise: don't even think about it.

replacing the plugs is not really that hard, except if you are extremely inept, you can google for the specs on the power supply etc, but i second shugs opinion. get a new supply.

in fact, youre swapping mainboard from at to atx, that probably means that you're also swapping ram and graphics...

so buy a new case with atx power supply, and keep the old box around, set it up as a second system. you can never have too many working comps in the house, never know when one might go tits up and you need to dl stuff etc.