Question : System won't boot from CD even though BIOS is set to do so

Trying to do fresh install of XP on a system ruined by viruses etc. Have backed up and now want to format disk and install XP. In BIOS setup, Boot Sequence is 1. IDE CD-ROM Device  2. Hard-Disk Drive C;
There are two drives on the pc, top one is DVD, bottom one is CD-RW.
No matter which drive I put the Windows CD in, it won't boot from it.
I don't get any message on the screen to boot from CD ... it just goes right ahead and boots from the hard drive.
What am I missing?

Answer : System won't boot from CD even though BIOS is set to do so

Did you try a different CD?  I know in another post you said you had 2 DELL install CDs.
Hit F12 on startup and you should get a boot menu and select CD from there.

The CDs may make you press a key to boot from them so make sure you are watching or else they will move on to booting from the HD.