HI I LOST MY MAC OS X STARTUP DISK AND I WANT TO KNOW IF THERE IS ANY WAY TO GET ANOTHER ONE IN ORDER TO RESTART MY MAC

Call AppleCare. Have your machine's serial number at hand.

Or use a retail version of the Snow Leopard install DVD.

Using the Snow Leopard retail install DVD is only possible for MacBook Pros older than March 15, 2010. First it is best to determine if that is a possibility to save the person the extra expense of buying a retail disk that may not work with their system.

Before thinking about booting from the original discs, you should first see if you need to just troubleshoot your system some other ways. It is always best to troubleshoot a backed up system, or one that you at least attempted to restore your data first into some form of useful mode, if it doesn't boot. For instructions on both, see this article: https://discussions.apple.com/docs/DOC-1992

The original discs are useful for a hardware test that shipped with your machine. While not a perfect method of detecting hardware issues, it can isolate many. If your intent is to install Lion, you don't need the original discs, if your system is working. See this tip:

https://discussions.apple.com/docs/DOC-2465

Applecare can be reached here:

http://www.apple.com/contact/phone_contacts.html

P.S. A reminder to Anais, please do not use ALL UPPERCASE. Those experienced with the internet would think you were shouting, and might take your remark as rude, and avoid responding to you if you continue to use it. It is also very hard to read.