To find the device name under Linux, start up a terminal, then type
ls /dev/sd* /dev/hd*
then press Enter.
This should give you a list of drives, such as:
/dev/sda /dev/sda1 /dev/sda2 /dev/sda5 /dev/sdb /dev/sdb1 /dev/sdc
You may also get an error, as it is likely that either one of the the /dev/sd.. or /dev/hd.. device groups do not exist. You can ignore this error.
How do you know which device is the HD24 drive? A few hints:
In the above case, /dev/sdc is the most likely candidate.
Under File->Recovery->Select device... you should now specify this device. In the dropdown box Choose device, either select the device name, or select --Use other device-- and manually enter the device name of the HD24 drive.