I have a 40 & 8 gb hard drives, when I install them in the computer it do not work. the motherboard powers on but the psu does not. but when I use them as externals, the pc can read it and its working. what could be the problem. please help.
your computer is behavimg so because it is trying to boot from the hard drives.
i guess that you have no windows installed in these drives, this is why you are getting this problem.
check if the drives are set to master, you will find the configuration on the drive itself.
if they are on the master mode, set them to slave mode. then should not be getting these problems.