Display Time

I'm pretty sure that doing so would require a change to the code used in the computer's BIOS. I've never seen a BIOS that had a user adjustable setting for that timing.

This option comes up before the operating system loads. The registry files have not been loaded into RAM yet - so no, it could not be a registry settings.

Could it be a registry setting ?.

NO

The decision of what device to boot from (CD or DVD) takes place in the BIOS. The BIOS has no knowledge of let alone the ability to access the registry. The only possible way to lengthen the selection delay would be with a BIOS option, if one exists. I have never heard of such an option. Don't even think about modifying the BIOS otherwise.