You can use third party softwares/tools to monitor temps of your GPU.
HWMonitor, lets you check the temps of almost all of the major components of your PC.
Or you can use EVGA Precision. It monitors your GPU temps only. It should have come with the disk whn you bought your EVGA GTX 570. Otherwise, you might as well download the latest version from their website. The ones from the disk, might be a bit old.