my computer not showing cd after install

Hi,
I did a repair from cd on a XP home pc. The repair was sucessful. I then installed a second hdd as a slave and formated it. The client e-mailed me and said the cd will auto run if you insert a disk but the cd does not show up in my computer. What shows in my computer is c: main drive e: slave drive and a: floppy. Any ideas on how to get the cd-rom shwing.
Thanks
Mark