I recently purchased a dell XPS 8300 to upgrade from an xps 410. As soon as i got the new computer I started putting in new parts:
Nvidia GTX 560 ti
intel sandy bridge i5-2320 3.0 ghz
rocketfish universal cpu cooler( I'm pretty sure its a refurbed coolermaster heatsink)
with those components the computer ran fine on the 460w power but I used a power supply calculator and apparently 460w was not enough for what I needed but it didnt make sense since the computer ran fine.
After finding out I needed more power I got a coolermaster 700w powersupply.
after installing this and connecting everything I pressed the power button and the fans on the gpu, cpu and case all whirl for about 2 seconds and then stop. No beeping, no funny noises. The mobo led is on so i know its getting power i just don't know whats causing the hiccups.
Make sure all of your connections are firmly seated (especially the 4+4 on the mobo and the 24 pin) and both 6+2 - just the 6 parts - are plugged into your GPU. Also, check your wires at the connections for loose connections (not unheard of).
If that doesn't work, you can go back to your 460W (note: PSU calculator give quite a bit of headroom since PSU's run cooler, last longer and provide more stable power if they are not at or near their limits)
For an idea of actual power usage, my i5 machine (see sig) while gaming with Seti@home also running draws 320W - it'll go to around 500W when I add another GPU.
howsit ya ok you will definatley need to upgrade you psu on that one, from what i experienced the bigger cards like the GTX 260 and up, they usually require a minimum of 550W power supply just for that card, if the psu turns off or the fans turn off then i would say that the psu cannot handle the load ( psu brands makes a difference ) then the psu is probably not powerful enough or its a DOA and faulty....replace with something with a bit more OOOMF!!! LOL