OK, it sound you still have a Grub prompt.
In a Grub prompt you can boot any operating system that has ever been invented on a PC. This is a big statement but here is how it work just for the Linux.
You can ask Grub to display any text file like
if you use a /boot partition, otherwise add "/boot" after "(hd0,0)".
You can type in the every line manually as displayed by the menu.lst to boot the system manually!
Basically every Linux will boot in a Grub prompt by
(1) A "root" statement specified the root of the Linux. If you are not sure it is the first partition with Type 83 if you do "geometry (hd0)" in a Grub prompt. It sound "root (hd0,0)" will work for you.
(2) A "kernel" specifying which kernel to be used and what parameters to be passed. You can type the exact line as displayed by the menu.lst
(3) Optionally a "initrd" statement. Just type the same line if it is in menu.lst
(4) Lastly in manual booting you need one extra statement "boot" as the green light for Grub to fire up the Linux. There is no parameter for the "boot" statement.