i dont know about system map... which distro are u using??
u can edit grub.conf in any editor.. try vim or vi..
u will find the initrd.img file in the same place u put the bzImage,i.e., /boot (this is in accordance with wat i have found in redhat distros & Ubuntu).
initrd.img will have some such filenames
initrd.img.2-4-5
initrd-2-4-6.img
etc
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