Kind of hard to give you a cable diagram, Roslyn, when you haven't stated what motherboard manufacturer and model number.
Or computer manufacturer and model number.
(Back of computer next to Windows product key; or up on side of computer tower )
So we'll wing it..............
Widetech the Max. A modular line of Power Supplies.
1) Main power cable;
It will be either a 20-pin ATX main power cable, or a 24-pin ATX main power cable.
The WTM (Widetech the Max) will have a braided thick cable, that will have a 20-pin connector, and a 4-pin connector.
Looks like this,http://www.playtool.com/pages/psuconnectors/connectors.html#atxmain20plus4
The 20-pin connector, and the 4-pin connector, should have a white arrow on the side. The arrows point to each other, when the two connectors are properly aligned with each other.
So, ATX main power cable plugs into Power Supply, (If removable), and 20 + 4-pin connector plugs into motherboard.
When the hooked end of the Lock, on the side of the power cable's connector; is over the Tab on the motherboard connector; the power cable is deemed to be plugged in properly, and tightly.
Orange wires are 3.3 Volts
Red wires are 5 Volts
Yellow wires are 12 Volts.
Black wires are Ground wires. (Also are Negative)
Note that the extra 4-pin power cable, that attaches with the 20-pin ATX power cable; has TWO Yellow wires, a Red wire, and a Black wire.
This way you don't accidentally somehow, plug the following power cable, in with the 20-pin ATX main power cable,
2) 4-pin ATX +12 Volt power cable:http://www.playtool.com/pages/psuconnectors/connectors.html#atx12v4
When Processors started using more power, than just the processor socket (Motherboard) could deliver, this power cable was brought out to help carry the load.
TWO Yellow 12 volt wires, and TWO Black ground wires.
3) 8-pin EPS +12 Volt power cable:http://www.playtool.com/pages/psuconnectors/connectors.html#eps8
Brought out for motherboards supporting multiple Processors, (CPU's), such as a server computer; but with processors needing more, and more power; is used quite frequently by motherboard manufacturers now.
NOTICE the power wires. The color code of the insulation of the wires.
FOUR Yellow wires (12 Volt), and FOUR Black wires. (Ground)
NOT to be mixed up with the following power cable,http://www.playtool.com/pages/psuconnectors/connectors.html#pciexpress8
This baby plugs into a GRAPHICS CARD (Video Card. Same/same)
A PCI Express graphics card, IF it uses one.
The PCI-Express x16 slot on the motherboard, is only capable of delivering 75 Watts.
This power cable can deliver UP TO an additional 150 Watts.
It is an upgrade of this power cable,http://www.playtool.com/pages/psuconnectors/connectors.html#pciexpress
The 6-pin PCI Express power cable was brought out, to provide more power for a graphics card.
So now you have the PCI-Express x16 slot on the motherboard capable of 75 Watts, and the 6-pin PCI Express power cable capable of 75 Watts; for a total of 150 Watts available for a graphics card.
PCI-Express x16 slot on motherboard, and 8-pin PCI Express power cable?
This power cable,http://www.playtool.com/pages/psuconnectors/connectors.html#eps4plus4
Is for a motherboard that uses a 4-pin ATX +12 Volt power cable, OR an 8-pin EPS +12 Volt power cable.
Is a combined power cable if needed, just like the 20 + 4-pin ATX main power cable.
This power cable is a SATA power cable,http://www.playtool.com/pages/psuconnectors/connectors.html#sata
Used to plug into a Harddrive, or Optical Drive. (CD/DVD drive)
IF your SATA harddrive has a provision on the back; to plug in EITHER a SATA power cable, AND a 4-pin Peripheral power cable; ONLY use the SATA power cable.
Using BOTH power cables will burn up the harddrive. May not happen immediately, but I ASSURE you it will happen.
4-pin Peripheral power cable, is also erroneously known as a 'Molex' power cable.
Molex was the first company with the CONNECTOR design. The name stuck. Kind of like calling an adjustable open-end wrench, a Crescent wrench,http://www.playtool.com/pages/psuconnectors/connectors.html#peripheral
[ IDE (PATA) harddrive shown in photo. Not a SATA harddrive ]
Note that between a SATA power cable, and a SATA data cable; the SATA power cable's connector is longer.
SATA power cable connector has 15-pins.
SATA data cable's connector has 7-pins,http://en.wikipedia.org/wiki/File:SATA_ports.jpg
Note the L-shaped opening of the SATA data cable's connector; and the L-shape of the motherboard connector.
The SATA power cable has the same L-shaped opening.
NOTE that color of connectors does NOT matter.
Could be green with pink polka dots.
It is the wire color code, and connector SHAPE, that matters.
[Applies to ALL cables, and connectors}
Sometimes the SATA power cable, and SATA data cable connectors; have a lock on them.
May not see it very well. It is usually a slightly raised bump on the connector. This is depressed with a thumb nail to unlock.
Unlock WHEN installing, and removing.
ALWAYS use the connector when plugging in, or unplugging a cable.
DO NOT pull on the wires.
(Even if you have to stand on your head, and whistle 'Dixie')
I lay the computer opening side UP, on a static free towel, on a table. Much easier to get to the cabling.
ONLY plug in the cables you need, to the Power Supply.
That's what Modular cabling is all about.
Gives more room when not using unnecessary cables, and more air flow through the computer case; for cooling.
I just installed a ThermalTake TR2 600 power supply. It is Modular Cabling also.
I'm willing to bet you didn't plug the Processor (CPU) power cable in.
Either a 4-pin ATX +12 Volt power cable, OR an 8-pin EPS +12 Volt power cable.
Make sure the Ram Memory is seated tightly also.
It get's bumped loose when installing a Power Supply.
No,.....you CANNOT just visually inspect, and let it go at that.
You HAVE to remove ALL ram memory modules ('Stick'), and plug them back in again; to be ASSURED that they/it are seated tightly, and correctly.
Well that about does it for me kid, post back in a Comment if you have additional questions.