Hello PandaCoins,

look for your nvidia 8800 gts at https://en.bitcoin.it/wiki/Mining_hardware_comparison

Try some options from there.

Also try to use http:// infront of the address.

Download http://www.cpuid.com/softwares/hwmonitor.html and monitor your gpu temp while mining.

The official max temp is 90 it should not be much higher then this, otherwise it will affect the lifetime of the gpu.