Some Ddos Tools you need to run
something like metasploit, and infect hundreds or even THOUSANDS of
machines with malware to successfully launch this type of attack. If
you're asking this question you don't have the skill to infect the
required amount of machines with your script, nor do you posses an
operating system that would allow you to launch this attack. You SHOULD
be using an operating system such as Linux Backtrack 5 R3, or Linux
Kali.
Again IF you're asking this
you do not posses the skill nor resources nor intelligence (no offense...