I have just received a G3 (Blue case), although I am not new or inexperienced to computers, I am am to MAC. I have the MAC OS 10 CD. I have inserted the CD in the Cd drive and the system boots from the disk. I follow the online instructions to the point where it states "select a destination volume to install...". The only thing on the screen is the indentification of the CD containing the installation CD. How do I select a destination volume. ALL drop downs at the bottom of the screen are greyed out. Thank you.