If you are installing Linux you can specify, on the last screen before it starts to install, where to install grub. The default is the mbr. There is a button called "advanced" I think it's called. Click it and put in the designator for the partition the /boot folder is on. It is usually the root partition of your Linux install if you don't have a separate /boot partition.
Let's say you don't have a separate /boot partition and your / partition is sda6. You would enter (hd0,5) in the installer instead of mbr.
If you have an existing install that you can't now boot into, use SuperGrub live cd to boot into it. Don't be tempted to fix it with SuperGrub, just use it to boot into the Linux install.
Using the same example as above, open a terminal and type:
Close the terminal.
You will now have grub installed to your / partition pointing to the menu.lst located in /boot/grub of your / partition.
Insanity: Doing the same thing over and over and each time expecting a different result.
Democracy is 2 wolves and a lamb voting on the menu. Liberty is an armed lamb protesting the electoral outcome. A Republic negates the need for an armed protest.