I can't put my computer back together!

So I have a really old computer, (I'm at work right now but I can get all the specs later if needed) I got a newer computer from a friend that is way better but not booting so I took it to try and fix it. It will need a reload of the system software but I need Vista or 7 and do not have at the moment. So until I can do that, my old one will not work anymore.

I took it all apart. I thought I knew how to put it back together if I needed to but I wasn't thinking I would need to. I took out all the hard drives so I could put them in the newer one, to find out the newer one only has sata connections and my hd's do not. I had 3 hd's connected to my old one and I'm not even sure which one had the OS now. Which really doesn't matter because I can reload XP on it if the darn thing would turn on. I'm getting no power at all.

There are 4 slots on the mother board and they all look the same. I've tried to plug in the power supply into each one and hook up one hd, but it still won't turn on. The power supply is brand new, installed about 6 months ago and was working fine before. I'm missing something. All the wires leading to the power button are connected as well. Would connecting the hard disk drive be necessary or completely irrelevant? Would the hd jumpers have anything to do with it? I took them out as well, that's why I'm not sure which one was which but I can't see that having anything to do with the power? I would like to get this thing put back together for the time being, any help would be appreciated, thanks in advance.

Its easy once you see it, so watch it:
The animated guide to Building a PC. Learn to build a PC from scratch with PCitYourself!

I've watched a few videos on You tube, (not nearly as good as that one) Thanks for that! I will check when I get home if I have all of this correct. I thought I had it correctly but I guess not. With 4 IDE slots, how do you know which one to connect the hd to and which one to connect the cd drive to? Does it even matter? This old PC has no sata connections.

When you try to turn your computer on you're not getting any power at all? No lights, fans, etc.

Correct wither. I though I had the power supply connected properly but I will double check now with the nice video patonb left me. As it is now, I get no power whatsoever, no lights no fans, zero. As I said it is pretty new and WAS working so I don't think there's anything wrong with it. I'm probably just an idiot and forgot something! :P

like plug it in. :D

On some mobo's, there's a switch to change the power voltage or frequency. Did you accidently switch it?

Do you have a circuit breaker such as a surge protector that could be open?

Did you loosen wires at the power on button or where it connects to the mobo?

The power supply doesn't provide power for everything on the board.

Hmmm, not sure about this switch you speak of, could be a possibility. There's a switch on the power supply for selecting watts but that's the only switch I knew about. No circuit breaker involved, and the wires to the power button are all connected (properly I think).

The switch will be on the power supply, not motherboard. Possibly 2, 1 is the one off, one is the 120/240V switch.

You need 2 plugs to be in for power. The 20/24 and the 4/8 pin.

IDE drives suck. As they need to be "switched" correctly.
Read this, PC Hell: Master/Slave Settings vs. Cable Select when Connecting IDE Hard Drives
It should explain it... I hate IDE.

My suggestion is to initially boot with no drives, and JUST CPU, RAM PSU. Then add in drives as it works.

Ok that's very helpful...I did not know you try to turn it on without a HD.

I still can't get it to turn on. I know the issue though.

As patonb said "You need 2 plugs to be in for power. The 20/24 and the 4/8 pin"

I can clearly see where the 20/24 power supply plug goes, but the 4/8 I have no idea! I have watched video's, and still can't find it. The plug has 4 connectors and I can't 4 pins to match it anywhere on the motherboard.

The 4/8 plug is typically up near the CPU, often "behind" the mouse/keyboard/USB connectors. If you can, post back the motherboard model, which is often printed in larger lettering right across the board in the middle.

if its your Acer still, i pouinted to it in the pic

Thank you everyone for the help. I finally got it connected properly and with the hekp of you all, it's running once again.

Glad to hear you got it figured out. What exactly was the culprit? Also, if you have a moment, click the "mark as solved" button.