Noob question! Is the Dimension E520 compatible with a DDR3 graphics card?

Thanks mate, brilliant answer

Very helpfull

I'll be sure to get rid of the ATI drivers and thanks for saving me the dosh :)

As for the power supply issue, i'm getting a thermaltake 250W additional power supply which fits into my empty drive bay, which will solely be used to power the card

 http://www.thermaltake.com/product/Power/PurePower/w0099/w0099.asp

I'm using lots of psu power already with additional recording equipment, so for 30 quid the thermaltake is probably best option

Thanks again SR45!

DDR 3 graphic cards will work just fine with that system. Your only consern is that the card has to be a single slot and not one of those wide double slot cards.  The 8600 GTS card is a fair card to have, it will fit and work with the current power supply. Your other issue is the 4 pin power connectors that are needed to hook up to the video card.  You do not have enough of them so the below solution will help in this matter.

Below link takes you to a site that sells a Molex power cable that will work for your system. Its a 6 pin to 4 pin connectore that eleminates the need for two 4 pin connections, only need one. The 6 pin end goes into the video card, and the other end ( 4 pin side ) goes into a free available 4 pin power input that comes from the power supply.

http://www.newegg.com/Product/Product.aspx?Item=N82E16812201004

Or…..

A SATA to 4 pin adaptor to convert those unused SATA connectors on your PSU to the 4-pin Molex connector instead.

http://www.performance-pcs.com/catalog/index.php?main_page=product_info&products_id=20580

Newegg has them as well for the SATA converters

http://www.newegg.com/Product/Product.aspx?Item=N82E16812263002