Sony PCG-XG28 Primary User Manual page 105

Click OK.
The device has not been recognized. Put the computer into System Idle
mode by pressing the Fn and S keys and resume.
If the device is still not recognized, remove and insert it again.
Check that the computer is plugged into a power source and that it is
turned on. Check that the power indicator on the front panel of the
computer is on.
Check that the battery packs are inserted properly and that they are
charged.
The computer may be in LCD (Video) Standby mode. Press any key
to activate the display.
The display mode may be in external display mode. Press Fn while
pressing F7 several times.
Press the Windows key and D key twice to refresh the screen.
Use the controls on your external display to adjust the image. See the
manual supplied with your display for more information.
Try restarting the computer. On the Windows taskbar, click the Start
button, click Shut Down, and then click Restart the computer.
If you cannot restart as described in the preceding step, you can
restart the computer by pressing Ctrl+Alt+Delete.
If the previous step does not work, press the power button and hold it
for at least four seconds. This turns off the power.