Perhaps I misunderstand, but the statement appears to be false.
My only copy of XP (Home) is a retail upgrade version (for the USA).
The CD is bootable. As far as I know, its only difference from the full
retail version is that I have to produce "qualifying media" to get it to do
a clean install (rather than an upgrade).
I haven't used the original CD recently, as I have prepared a version with
SP2 "slipstreamed" onto it. (The copy is also bootable.)
In the event that the OP's PC can't boot from its CD drive, it is possible
to download a utility that creates a set of six floppies to begin the XP
installation by booting from the floppy drive:
http://support.microsoft.com/default.aspx?scid=kb;en-us;310994
I've never used the boot floppies, though, as the oldest hardware I've
installed XP on supported booting from a CD drive.
Address scrambled. Replace nkbob with bobkn.