You may find it easier to use a GRUB boot floppy.
Go back to the MEPIS install utility, and have it install GRUB to your root partition, instead of to your MBR.
Then go to the following link to make a GRUB boot floppy:
http://www.mepislovers-wiki.org/inde...ot_floppy_disk
(Make sure that your BIOS is set up to boot first from a floppy).