Assuming it's Mac OS X, since it's an IDE disk this is likely.
Within Ubuntu/Linux/FreeBSD try something like
mount /dev/hdaX /mnt -t hfsplus
Where the a corresponds to the first disk, b second disk, etc.
The X is the partition number.
If my own system is representative it should be
mount /dev/hda3 /mnt -t hfsplus
It's the 3rd partition in the table below in this out of the box Mac OS X set-up.
Partition map (with 512 byte blocks) on '/dev/rdisk0'
#: type name length base ( size )
1: Apple_partition_map Apple 63 @ 1
2: Apple_Free 262144 @ 64 (128.0M)
3: Apple_HFS Untitled 312319590 @ 262208 (148.9G)
4: Apple_Free 10 @ 312581798
Device block size=512, Number of Blocks=312581808 (149.1G)
DeviceType=0x0, DeviceId=0x0