From the grub> prompt you should be able to boot your system if you know your partition setup and the name of your kernel. If you know the name of your kernel (possible "bzImage" you can type
and that'll spit out something along the lines of "(hd0,0)" which is your boot partition, that is, if it can find the kernel. If that works, or if you know what partition the kernel is on, you can type this:
replacing (hd0,0) with the partition your kernel is on, and bzImage with the name of your kernel. Also, replace hda2 with whatever your root partition is. If it gives you the message saying the image is found type:
kernel (hd0,0)/boot/bzImage ro root=/dev/hda2
and cross your fingers
Just a quick note on partitions, /dev/hda1 is primary master IDE device, partition one, /dev/hda3 is primary master partition 3, etc. But grub's scheme is slightly different, (hd0,0) is primary master, partition 1, and (hd2,1) would be secondary master, partition 2.
Hope that helps you out, and good luck with the tux