I am presentley running a GEFORCE 4 MX440 64MB NVIDIA DDR (AGP) card on my computer with success. However I have just purchased a brand new GeForce 6600GT card. On starting my computer with the new card there is a long beep from the computer - and no display at all. Please could someone help me with this, thanks

Did you uninstall the old drivers for your old card and(I have to ask) did you take out the old card? Also, what kind of power are you working with?

I unistalled the old driver...I changed the cards over..and nothing, power? how can i check what power iam using?

It should be written on your psu. Here's an example of a bad psu (courtesy of Kirock)

Give us the wattage and the amps on the 12 volt rail(underlined in the picture)

I have a CODEGEN 300w 12v - 13A

Having looked at my manual more closely, it recommends a 350W ...I take it this is half my problem?

I am also supplied with a a small cable with a four hole female connector to each end, I can see where this fit's on the AGP slot, but there appears to be nowhere on the card?

Do I need to plug this in?

Yup, you need to plug that in. You have to connect it to your psu. I dunno if you should worry about the 300w psu, I'm running a 6800gt fine here with a 305w psu, although I'm reliably told it will blow up any second.