A couple of things spring to mind
Firstly make sure that you have set the boot order correctly in the bios ie: make sure that it is set to boot from the cdrom drive before any other boot devices.
Secondly I don't understand why it will only read a dvd and not a cd, as all dvd drives will read a cd, unless the cd is damaged or the drive is faulty or possibly one or both of them need cleaning.
Thirdly I presume that the Windows XP home cd is full version and not just a recovery cd as most that are supplied with computers nowadays are just recovery cds.
As you say it happens with other install disks as well I would suspect it is either of the first two options and the most likely of any of them is the first.