Anybody ever do graphics card upgrade for a Gateway FX 540S?

Really hoping somone may have done an upgrade to their FX 540S to help me out on this, or someone who can tell me exactly where to connect the additional power source to on the computer side..
Doing a graphics card upgrade for my Gateway FX 540S, from the existing Nvidia GeForce 8600 GS to a GTX 660. I cannot figure out where to get the additional power source on the computer side to go to the 6 pin card port. Done a lot of research without any results. There are some vacant connectors in the case, couple of vacant six pins on one end, and a vacant plugin connector near the card.
I also found some info that said you can't change the existing card out on this Gateway model. Nvidia support said it will work, I just don't know where to connect the additional PS connectors. Thought this upgrade was a slam dunk, just don't want to connect it up wrong and fry something.
Appreciate any help.

Well when upgrading GPU's in a manufacturer-made computer, you almost always need to upgrade the PSU with it.
If I'm not mistaken, the 660 has 1x6-pin power connector. If your PSU has a cable coming out of it with a 6-pin connector, try plugging that in.
You'll also need to make sure your motherboard has an applicable x16 PCIe port.
Maybe take a picture or two so we can get a good idea what we're looking at.

Thank you for your time on this! The PSU for this Gateway FX 540S is a 700w. I only play Wow, so probably not going to ramp the GTX 660 to its max...stats...149w normal use... 292w max on high end game. I did a calc on Newegg's Power Supply calculator for my existing setup and it is using 378w. So, looks like there is plenty of room for the new card.

I have a link to some photos I took, pictures I always feel are the best to describe the situation. The molex connector does come from the PSU and only has a small fan to the motherboard tapped to it. I tested the Molex connector with a voltmeter... the yellow wire is 12v and the red wire is 5v. The male 3 wire Molex to 6 pin adapter I got with the new card has 3 wires, yellow, black, brown, which would connect yellow to yellow on the computer female Molex. (There is not a pin on the Molex adapter to correspond to the 5v red wire on the computer Molex connector.)

The two vacant 6 pin connectors P20 & P25 have 3 blue (not a true blue) on top and 3 black on the bottom and come directly out of the PSU with nothing attached. I tested the voltage for both, all 3 blue wires on each 6 pin have 12.2v per wire.

So, my inclination is to go with the Molex instead of messing with the 6 pin? Or would the 6 pin be the preferred for the 6 pin port on the new card? Guess I would need to confirm that with a Nvidia tech maybe? Although looking at the six pin on the adapter, the yellow (2) wires from the 2 Molex male connectors are on the top side of the six pin and the brown and black wires go to the bottom of the six pin. ( I am assuming that the brown wire is a ground, although I don't see it listed for voltage wire color coding on computers) Given that configuration, either of the computer 6 pins would work, but not sure about the middle 12v wire if it is needed on the card or might cause a problem. The port on the card has six pins, but the Molex to 6 pin adapter does not have a pin in the top middle, just the 2 outside which have the 2 yellow wires going to them.

One other thing, the card for the S-video, TV, audio ect. that is directly above the graphics card, will be in the way of the new card (due to fans on top) if I put it in the same slot as the existing card. Can I put it in the vacant slot below where the existing card is? If not, can I just remove the S-video, TV, audio card, as I am not using it for anything?

Dang, seems like I am doing overkill on this, but learning quite a bit. Should just step up and build a new computer for the graphics card haha.

Here is the link for the photos: http://www.flickr.com/photos/42280644@N08/sets/

Thank You!

Well, firstly, turn off your system, unplug the PSU cord, and yes, turn off the PSU as well. (there should be a off-on switch at the back of your PSU. [don't get this confused with a little red switch, that red one is for PFC [power factor correction], don't mess with the red one.)
Then, open up your case, and locate your current GPU.
Fiddle with the little white hinge on the PCIe slot (try lifting it or sliding it) until it goes loose, then pull out your card. This may take a little force so don't be scared, but be careful too.
grab your new card, and whilst taking appropriate ESD precautions, insert the card into one of the longer PCI slots, preferably the one closest to where the CPU is. This will probably take a little bit of force, and you may hear a click when you push it in. Then, screw in the card's bracket to the case, to fasten it.
Then, find this cable coming FROM your Power supply, and insert it into the card's power connector.
(don't bother with using any adapters)
You only need to use one of the 6-pin connectors, you can leave the other one just hanging there.
The cable only goes in one way, so don't worry about screwing anything up.

Once it's all in, give it a look-over, to make sure you didn't do anything wrong.
Then put the AC cord back into the power supply (which you unplugged earlier)
Turn the PSU back on.
Then punch the power button on your case, and everything should be good.
When the computer turns on, the screen will be all distorted, like the resolution will look all whacky. That's normal.

Then it's a simple process of downloading drivers (to make the screen look normal), and you're good to go.

As for the S-video card, it's up to you whether you want to keep it or not, but if it fits in a vacant PCI slot, then go for it.

If you already knew how to do all of that, bummer for me because I just wasted a good 8 minutes of my life.
If not, yay.

If you have any other questions feel free to ask.

Thank you for your reply and help. I just am having a problem knowing if the idle 6 pin connector is what I should connect or the idle molex. Can't find any info or help from Nvidia support as to the new card six pin port configuration. If it is okay to just connect the idle 6 pin from the PSU, which has 3 12v connections on the top row of the pin, and the 3 ground connections on the bottom row of the pin. If the 6 pin port connection on the card is the same configuration, obviously it is the way to go. Could just connect it and see what happens, but sure as heck don't want to fry something.

The six pin connectors labeled P20 and P25 should work for auxiliary power for your video card. (obviously, do not force them if they do not fit. If you look closely you will see that each socket is surrounded by differently shaped plastic pins) Yes, the x1 audio card can be plugged into any x1, x4, x8 or x16 slot. therefore it can go into either the yellow slot or the second blue slot in IMG_1425.

Forget molex, or any other adapter. it's useless.
Follow the exact steps I said above and you'll be fine.
It's ok if you have a split 12-pin cable, and are only using 1 of the 2 connectors - you don't need to have the other one plugged in to anything. You don't need to worry about Volts or rows or Nvidia support or molex or anything. It's a very straightforward process of inserting the card into the motherboard, sliding in one of the two 6 pin GPU connectors to the card's 6 pin power connector, and booting up the system.

chill dude -- he asked for help because he doesn't understand. Don't pressure him.

I'm very chill, thank you.
Trying to explain it as simply as possible

Thank you both phillipnolan and xcylent! I know it is relatively simple, just without a schematic for the port on the new card side, I just wasn't sure. I am a retired Power Lineman and have seen some pretty amazing high voltage flashes during my career. 115kv to ground is unbelievable! I appreciate your time and help. Will probably put it in tommorrow.