help reguarding cpu and Mbo upgrade

In general, im trying to tranplant a classic slot A athlon 700mhz, into a box where i took out a K6-2 500mhz. I am not sure what version atx power it has, i know its 250 watts. I thought 250 watts would be the minimum so i tried it. I power the machine up, and only the cpu fan is blowing, no hard disks or cd roms. No signal to the monitor. I disconnected the ide cables from the hard disk and cd rom, and i hear the hard drive spinin, and lights from the CDROM when i turn on the machine. When i try to connect the IDE cables back to the disks and cd rom, to the motherboard they dont power up(i checked, they are master and slave). Anyone know of this problem? is it a power related? thanks for anyone willing to give this a thought. have a good night guys.