most of the windows cds will check for an existing OS when booted from the cd.
if one exists, it'll then display the message to boot from cd, otherwise it'll just boot directly into the installer.
however, some bios also have something simlar to boot from the cd, so in some cases, u have to do it twice.
i would try unpluging the hd and just seeing if the installer actually starts.
u could also try to disable the hd as a boot device in the bios, so it'll only try toboot from the cd
if one exists, it'll then display the message to boot from cd, otherwise it'll just boot directly into the installer.
however, some bios also have something simlar to boot from the cd, so in some cases, u have to do it twice.
i would try unpluging the hd and just seeing if the installer actually starts.
u could also try to disable the hd as a boot device in the bios, so it'll only try toboot from the cd