How can I find out what /dev my usb dvd drive?

I'm going through the process of installing AsteriskNow on an old pc of mine. I've got a usb dvd drive which plugs in to 2 usb sockets (I'm assuming one is extra power). The machine reads the disc and boots fine, but then it says it caot find the Kickstart file and asks for the directory where the file is.

It prompts me for cdrom:/kickstart-raid-asterisk13.cfg - however this caot be found. There is one hard drive installed in the pc plus the 2 usb coections for this drive.

I've done some googling but some people use sdb1, sdb2 etc and others say sda1... How can I find out - I caot get in to any other prompts.

- - , .