Multiple Booting Scenario
 

ok, right now I have RedHat 9 and Xp being dual booted using Grub - in a few days I want to add Windows Longhorn to the mix. Going further with this, in order to get longhorn on my system in the first place I need to format my Windows partition and create a smaller one for Longhorn. My questions are - will Grub recognize windows after the format, and how do I get Grub to recognize Longhorn?

Well, I'm not sure about Longhorn(and not sure how you got it) but I know all previous versions of windows will blow away grub when they are installed. After you install Longhorn and reboot you will probably find yourself without grub and you will be directly booted to Windows.

Make sure you have a boot disk created. Then after you install Windows boot into linux and re-install grub so that it takes over the bootloader again. Then appropriately configure grub.conf for the windows and linux boot partitions.

now, this is going all out newb...but how do you go about reinstalling grub?

Check out the gentoo grub install instructions. The only thing you won't have to do is 'emerge grub' being that you already have it installed.