hi,
i have two os, vista and ubuntu linux.
i want to change the boot order. can anyone please help me in this.

I guess this issue must have been taken care of in LQ.
You could change the boot order in file menu.lst in /boot/grub directory.
You need to be root even to open the file so very obviously you will need to be root to edit it. You should be fine using sudo

In /boot/grub/grub.conf you will find the line "default=0" perhaps. this refers directly to the "title" line where 0 is the first number and 1 is the second and so on. If you want to swap the boot order, you can either change "default=0" or whatever to "default=1" or whatever, or you can move the chunks of boot stuff in your grub.conf file. Since you are a beginner it would probably be easier to simply change the default boot number.

I would save your grub.conf as grub.conf.orig just in case you make a mistake.
(cp -p grub.conf grub.conf.orig).

All this is done as root BTW or in ubuntu "sudo su".