ATI Radion 4850 issue

i have just replaced my Nvidia 8600gt with the ATI Radion 4850 mentioned,,, my psu is 500w in my HP elite an Asus mobo,, Q6600 chip and 3gb of ddr2 @ 800Mhz on windows vista ultimate ,,,
i uninstalled all the nvidia stuff using revo uninstaller driver sweeper and esuing cleaner to get all the left overs,,,, put the new card in securely and also connected the 6pin to molex adapter to the card and the power supply,,,, now this adapter has 2 moles connections,,,, do both of these have to be connected to a power supply or just the 1 like i have done with mine,,, the reason i ask is,, when gaming with head phones i hear a constant crackling noise,,,, even when not playing on cod4 ,, say i open the start menu and move the cursor up and down the options on the right side like over computer,pictures etc,,, i hear a vibrating noise,,, like waving a light saber around,, that humming noise (this is the only explanation i can think of,,,lol)
all sound and graphic drivers are up to date,,, any help would be much appreciated and thank you for your time.

hi,,, i have now connected the other molex terminal ,,, thanks,,,, as for the head phones i have tries several sets,,, 3 sony 2 jvc and it makes the light saber noise when moving the cursor over things ,,, whats making me think its to do with the card is,,,, my older nvidia is now fitted in another machine with no issues as was the same when fitted in this pc,,, and when i open a window or a box or drop down you get the voom of the light saber waving past so to speak as the window/box opens,,, sounds a bit crazy i know,,,, and when im on cod4 there is a constant crackling noise when playing,,, doesn't put me off my aim but its there and is bugging me now

Double check any and all hardware and connections to the motherboard. The card you just put in is twice the size of the old one, and it would be very easy to inadvertently bump something during the installation and knocked it loose.

P.S. you say you have a 500W power supply, if you don't mind what is the make and model number of it?

Does your card have the 6 pin connector? Does your PSU have a 6 pin plug in connector? If so, just plug in the 6 pin connector to 6 pin port on the GPU. Almost all PSU have two of these and some have 4 but the bare minimum is 2. You would only use the molex adapter if you didn't have one of those 6 pin leads. This could be part of the reason your getting feed back in your head phones by using this adapter.

hi guys,,,, did a bit of swapping around,,,, plugged my head phones into the jack port at the back of the pc and there are no darth vader noise from there at all ,,, so when i get chance i will open the case up and trace the wire from the mobo to the phono jack port in the front of the pc checking all connections as recommended,,,, i will also get back with makes and model of the psu,,,,
thanks for the help all.