you can load the kernel manually if you know that it's there for true...
Code:
grub rescue>root=/dev/sdX # with /boot partition
grub rescue>linux(or kernel depends of your grub version) kernel_image_name.img
don't forget to use <tab> to can see available options...
you always can boot windows reinstalling grub from Live CD, it makes update and auto-detects windows partitions...