How to modify the boot option in grub menu

In Condition of having dual boot option in the system/laptop we have mess in selecting it every time.

Here are simple steps to modify it.

Steps:

1) Login to the Linux flavor you have.

2) Navigate to the path /boot/grub

3) you will find the menu.lst file, open it in any text editor for your comfort.

  The booting option will take decision based on the number in the default = "";

  if its 0 the bootloader will boot the first OS you have  i.e Example: centos

 So if you have 3 OS installed in your system you can use the following numbers in     default options.

Eamples:

 default = 0  <= to boot the first OS shown in list.

 default = 1  <= to boot the second  OS shown in list.

 default = 2  <= to boot the third  OS shown in list.

4) Modify the option you need and save it.

5) Now reboot the machine now you will find the OS that you need to boot in as default.