GRUB for windows while not having a Linux root partition?
You can install GRUB from pretty much any Linux LiveCD.
However, for this to work GRUB needs a partition in which to store image files and configuration files (e.g. menu.lst).
This can be any partition. However, GRUB does not support NTFS. So these files need to be stored on a FAT32 or Linux partition. If you don't have one, you just need to create a small partition (8MB will suffice).