OSS doesn't see WinXP install CD

The DD docs say this is how to add a new OS:

8.2.2 Installing another Windows on a separate partition
• Prepare a free primary partition for the new Windows system. DONE
• Set the prepared partition active for the new operating system.
When installing a new OS from CD, select the CD item in the Operating systems area of the Acronis OS Selector main window. Then right-click on that item, select from the context menu Operating System Properties → Partitions and flag the partition you want the OS on as Active. DONE
• Reboot and ***select your CD or floppy bootup from the boot menu***, having inserted the disk with the OS distribution.

But that last bullet isn't doable...on restart, the WInXP install disk isn't shown as an option in OSS. When I boot using the HDD and reopen OSS, the CD-ROM entry I created is still there. What's going on?

Thanks,
Jim