graphics power cable

[Funnyhat29]

I currently own a pc with an amd a8-6600k and 8gb of ram, powered by a 500w psu. I am looking to upgrade it with an nvidia gtx 660. I bought the pc pre built and there doesn't appear to be a cable for a graphics card in the case. Is it possible there isn't one or could it be plugged into something in the computer that I may not know about? Finally if there is no cable would it be possible to get one.
thanks in advance

 

[dovah-chan]

Since you bought a prebuilt PC, one of the prime components they skimp out on to save cash is the PSU. You'll need to upgrade it if you wish to get a GTX 660, but if you get a GTX 750 (Ti) you could get by without buying a new PSU as it requires no PCI-E power pin connectors and has relatively low power consumption while maintaining very strong framerates at 1080p.