Do I need to plug in the PSU into my 8800GTX?

If your 8800GTX has an external power connection on it, then yes you must connect it to your PSU. To compare the performance of the 2 GPUs just look here:

http://www.tomshardware.com/charts/

Find your cards in the charts and compare them. Good luck!

Yes and yes, the GTX will not run unless you plug in the auxiliary power connector and it's also way better than a 9400GT.

Where can I get one of these auxiliary power connectors? I have a PSU which doesn't look like it has any outputs. Its just a big solid silver box with wires coming out of a 2inch hole. If its not possible to connect a 8800GTX, which is the best card that doesn't require a auxiliary power connector?
Thanks for the help guys.

Do you not already have the GTX then?

I do not, but my friend is selling his for 20pounds.

Given the direction this discussion has taken, you better make sure your PSU is sufficient to meet the power needs of the 8800GTX. What make/model of PSU (should be on a label on the side of the PSU) are you using?

If it's a working card then for £20 it would be worth upgrading your PSU for IMHO.

My PSU is a 450W. Whats a IMHO, and what are IMHO, and how much are they?

IMHO = In my humble opinion.

Need more than just 450W. That is its wattage level. What make and model is it?

IMHO = In my humble opinion.

IMHOs are generally free!

[8-)

TURBOLINK ATX-CW420W 12V.

Depending on which 8800GTX it is, 640MB or 768MB, it will use between 125w and 160w which is about the same as a GTX460 and a 450w is all that is recommended for one of those.

Haha, thanks for your help and opinions guys  .

It's about time that I got paid for mine so the cheque had better be in the post or there will be... Trouble!  

Ok so about the auxiliary power connector, can I connect one to my PSU or not?
And I haven't got a HUGE budget, but about 60pounds max for a card?

You should be able to pick up a Molex to PCI-E cable at a local computer shop or order one, but to be honest, that appears to be a generally weak PSU. I am not sure how far 40pounds will go (assuming you spend 20 for the GPU), but I would look for a better PSU as well. I would recommend a 500W or better and one from Seasonic or Antec.

Misco lists this one in your price range:

http://www.misco.co.uk/applications/SearchTools/item-de...

However, if you could swing it, this one would be much better:

http://www.misco.co.uk/applications/SearchTools/item-de...

COLGeek big reps to you! I'll prob be getting the Antec one, and might sell my build which I currently have. Bought it in America for $500, with these specs:
740G Motherboard
9400GT 512mb
Windows 7 HomePremium
Athlon 240
4GB DDR2 800Mhz RAM.

Should I keep it, or should I just make a new build overall.

The system looks okay to me, you could go to a stronger CPU and keep the rest and have a system that will serve you well for a couple of years. Go to your mobo manufacturer's website with you model of mobo and look for the CPU compatibility listing. I would guess you can drop a quad core CPU in there and see a pretty decent performance up tick. Add the 8800GTX and a solid PSU and you will be set!

Good luck!

OK, one more thing. How much will a fairly good quad core cost?

Thanks for everything COLGeek & mousemoney, 2 very helpful people.

Depends on the model. Check these out:

http://www.misco.co.uk/applications/factfinder/search.a...

Am I correct to assume you are in the UK?

Yes, im from the UK.
OK, that seems a fair price. I'll prob get one when they are on sale or something.
Also, about my AMD 740G Motherboard, I'm trying to find the CPU compatibility listing, but without success. Any chance you know where its located?
http://www.amd.com

What's the make and model of your motherboard? Download and run CPUz if you are not sure.

I'm not on it at the moment, but when I get on it I will update.
All I know at the moment, it's a AMD 740G Motherboard. (According to the leaflet I got from Tigerdirect when I bought it in the US).

CPUz will give you the info needed to then find out what CPU's the board supports.

OK, thanks for that.
One more thing, I know its in the wrong section but I'm just gonna make it quick.
I was my PC to work wireless like a laptop does. I have a Modem downstairs (Orange Livebox), what do I have to buy to get me connected to it upstairs, while the modem is downstairs. Is it one of those dongles? What are they called? Thanks!

A PCI wireless card is your best bet, it's fitted internally and just has a little aerial on the back.

OK, im gonna have to get one of those.
By the way, just got home, downloaded CPUz and this is the Mainboard:
GA-MA74GM-S2 CHIPSET ATI SOUTHBRIDGE AMD

Here is the CPU support list for that motherboard.

Hi,
You obviously know a great deal about the 8800GTX. May I ask if you also know the pinout for the auxiliary power connectors or where I could obtain such information?