dvd bootable

For the first part, simply try boot with the bootable DVD.

To create a bootable DVD, the following provides a step by step process:
http://www.cyberciti.biz/faq/creating-generating-rhel-linux-bootable-cd/

Depends on what you are trying to do.

More information required.

If you are trying to create a bootable DVD have a look at these instructions.

http://cdburnerxp.se/help/Data/bootdisc

You may understand that I am in windows now xp is my os..
at this point how can I make the dvd bootable please..

If the dvd is not bootable, you can't make the current disc bootable, but you can create another disc that has the same stuff on your current disc and make a bootable disc with this matterial. To boot up to the dvd you may need to change your current boot order of your computer so it chooses booting from the dvd before it boots to the hard drive. For this to happen you will need to access the bios of your computer, In the bios you should be able to see the boot order and you can change it so that the dvd is on the top. Sorry about the general instructions but it is totally imposible to tell you how to enter the bios to change the boot order of your computer unless we have more information. Such as computer manufacuturer and model number, and is this a laptop or desk top. etc

Since you were in Linux zone, I assumed that you wanted to make a bootable DVD in Linux

In Windows XP you can follow the instructions at this link
http://www.howtohaven.com/system/createwindowssetupdisk.shtml

can it be you are asking how to set the PC to boot from CD/DVD?
that you should select in the BIOS - in BOOT Priority Options, and set DVD as first boot device