Just wanted to be sure, it sounds too simple, but I can't tell you how many times I have found this.
The flip switch on the back of the tower, be sure it didn't get switched over to the "0" position, it should be on the "-"
If you get the computer to turn back on then I hope the following may be of some help:
The wide wire set, is the IDE connection that connects it to the motherboard and the 4 wire set is the power you get from your power supply. Every hard drive needs both the power and the IDE connection, unless you are using SATA, which you don't need to worry about.
Be sure each hard drive has the wide and the 4 wire connections. Then you need to set the jumpers correctly. As for you error, there is a possible fix but I don't know if you would feel comfortable with using it. Maybe a friend could assist you.
You may have a bad wide IDE cable or you may fix it with:
Method #2 in the middle of the page:http://support.microsoft.com/kb/297185
I have successfully used this.