If you want to remove a hard drive safely while the appliance is on, use the Safe Removal procedure described in Safely Removing Hard Drives.
To remove a SATA hard drive
If the desired disk tray's Tray Open Button indicates that the disk tray is locked (that is, the groove is horizontal), then unlock the disk tray by using a flat-head screwdriver to turn the groove until it is vertical.
Press the disk tray's Tray Open Button.
The disk tray lever pops out.
Pull the lever outwards to remove the disk tray from the C400.
Flip over the disk tray, and remove the mounting screws from the disk tray.
Remove the hard drive from the disk tray.
Slide the disk tray back into the C400.
Press the disk tray lever back into place, until you hear a click.