"not cleanly unmounted" devices when rebooting

[Hector Akamine <akamine@example.com>]

Hi all,

Almost every time I reboot my PC (using shutdown, reboot or
Ctrl+Alt+Del) I get a "/dev/sda5 was not cleanly unmounted, check
forced" message, and linux proceeds to check the HD. I think any of
the configuration files is missing a line to unmount the drives before
restarting. Where and what should I put to avoid this?

Thanks in advance