Sometimes Hal mounts partitions on your hard drive relating to test installs or other OSes which you don't want available in pclos. This can be stopped by giving each partition a mount point and setting its noauto flag, but that's fiddly if you have to do it for every partition created elsewhere.
An alternative is to tell HAL to leave sata and ide devices alone unless they have removable media (eg optical drives).
Put the following in a file (as root) and store it at /etc/hal/fdi/preprobe/20-nomount-hdd:
<?xml version="1.0" encoding="UTF-8"?>
<!-- store at /etc/hal/fdi/preprobe/20-nomount-hdd -->
<match key="storage.bus" string_outof="sata;ide">
<match key="storage.removable" bool="false">
<merge key="info.ignore" type="bool">true</merge>
HAL will now ignore SATA and IDE devices which don't have removable media.