Ransome :
Why building with the system plugged-in power in the first place?
Seems un-necessarily risky for both the components and yourself.
It should ALWAYS be plugged in or its not grounded. You plug it in and turn off the switch at the back which disconnects the hot line, so all that's connected is ground, which is connected to the case, which you connect your wrist strap too. Any charge gets drawn through to ground.
Realistically there is no risk even if the switch were on, the pins are recessed and there is no power through the lines till you turn it on via the board. Standard practice in a lab with actual sensative components is to connect your wrist strap to the ground line of a plugged in bench supply. That's why they have banana plugs on them
Ry4n :
I will be standing on carpet, and the case will be on a Wooden table, So will it be ok to stand on the carpet as I will be wearing a anti static wrist strap.
Yes that's fine. The strap will drain any charge build up to ground. Rubber soled shoes would also prevent you from picking up a charge from the carpet