You can use a 4pin just fine, I have been doing so for nearly two years on mine,
just make sure the plug goes into the correct (usually the lower) four socket holes on the 8pin socket,
although as Heny said, you will find overclocking etc more stable with an 8pin from the psu, i wouldn't use the connector shown though, I'm almost certain thats intended for graphics cards, not the cpu line
Won't be overclocking that Dell.
It's a molex to EPS adapter, notice how the yellow (12v) wires are on the clip side of the connector ?
Better off with an ATX to EPS adapter, if an 8 pin connection is required for the board ( the stock psu does come with an 8 pin, and some boards won't boot without it )http://www.newegg.com/Product/Product.aspx?Item=N82E16812119267