Boot from your hard drive at the grub prompt
The grub interface itself is pretty powerful. If you've deleted it's
configuration files, you can probably still manually configure it and
boot regardless. If you have the "grub> " prompt, this should be
An example is:
grub> root (hd0,0) grub> chainloader +1 grub> boot
This says to look in the first partition of the first hard disk (hd0 == first IDE disk) for the next stage of the bootloader. If your Windows installation is on the 2nd partition of the first hard disk, it would obviously be (hd0,1).
Found the above on this page: http://www.cybertechhelp.com/forums/archive/index.php/t-26320.html