jjbuchan: You can also run the grub “find” command first, if you are not sure where your /boot is located:
grub> find /boot/grub/stage1
grub> find /grub/stage1
Use the first “find” if /boot is part of the “/” partition and use the second “find” if you made a separate /boot partition. Or just run both of them if you’re not sure.
Grub numbering and other Grub concepts can be confusing in the beginning, so look at the Grub Manual if something isn’t clear: http://www.gnu.org/software/grub/manual/grub.html
Whatever you do, try following Paul7's instructions before you try anything drastic, like reloading windows or linux.