Acer AT150 F1 - Manual (Page 120)

5 System troubleshooting 108
Verifying the condition of the storage devices
As POST determines the system configuration, it tests for the presence
of each mass storage device installed in the system. As each device is
checked, its activity indicator should turn on green briefly. Check the
activity indicators for the hard drive(s), DVD-ROM drive, and any other
device you may have installed.
If any of these indicators fail to light up, refer to related problems
listed in the “HDD activity indicator does not light.” on page 109.
Confirming loading of the operating system
Once the system boots up, the operating system prompt appears on
the screen. The prompt varies according to the operating system. If the
operating system prompt does not appear, see "No Characters Appear
on Screen" on page 94.