DVD drive reads DVDs but not CDs

I recently installed a new hard drive in a friends PC. Since then, he's
had trouble using the DVD drive - it doesn't read CDs.

System configuration:
IDE Primary Master Samsung SP1213 N hard drive -Windows Xp SP1
IDE Primary Slave - None
IDE Secondary Master - Toshiba DVD-ROM SP-R1002
IDE Seconday Slave - Western Digital WD 600 hard drive

The Samsung is the new drive and Windows was installed onto it using the
CD drive. The old drive was then refitted. Due to the short
lengths of IDE cable in the machine, the above was the only
configuration possible.

I've checked all the jumpers and they're configured correctly for this
set up. Then tried removing the slave hard drive but that didn't fix
things. And all the drives are correclty identified by the BIOS and show
up correclty in Device Manager and My Computer.

Now I'm stumped for ideas and my friend would like a working computer back.