XP installs from a CD, Vista installs from a DVD.
CD & DVD use different heads to read the media.
It is quite possible the DVD read head is dirty or damaged in that drive.
Try a cleaner, if that fails, you may need a new drive.
--
A Professional Amateur...If anyone knew it all, none of would be here!
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"MarcD" <> wrote in message
news:8C9F34C5-01F2-4DB1-8525-...
> The disc can be read by a similar model machine. Mine can both read and
> boot
> from an XP install disc, but the Vista DVD isn't seen at all (not within
> XP
> nor on bootup). There are no firmware updates for the motherboard or drive
> which are more recent than what's already installed.