For power button look for the series of pins for reset, hdd light, .. that stuff. Sometimes (most of the time) the board will even label it for you with the polarity.http://www.msi.com/index.php?func=proddesc&maincat_no=1&prod_no=1740
Ok usb goes into the slot next to the fourth pci-e 16x connector. It's right next to the black ide connector. I believe there is a usb1 and usb2 labeled there but I'm old (32) so my eyes are going bad on me
And really my eyes are going on me yet the picture is blurry but it might be something near the side facing sata connectors.