Model: SGT P100
First, remove the SD Card and sim card. Press the Power button +Volume Up at the same time for at least 10 seconds. Release the power button when the Samsung logo pops up, but continue to hold the Volume Up until the recovery screen appears.
Use the volume buttons to navigate the menu and select one from the four options as indicated on the picture above, press Home to choose the selection. I suggest that you simply reboot, this alone might do the trick.
The said procedure resurrected my tab:) Good luck!