You can boot your system with any live CD, Debian, Fedora, anything. Once you've started the live system, you'll have to
chroot into your installed system. Let's assume
/dev/sda is the live CD and
/dev/sdb the disk your system is installed onto.
You'll have to determine what your boot and root partitions are. Let's assume
/dev/sdb2 respectively. In a terminal, type the following instructions, as root:
mount /dev/sdb2 /mnt
mount /dev/sdb1 /mnt/boot
for DIR in dev dev/pts sys proc; do mount --bind /$DIR /mnt/$DIR; done
chroot /mnt /bin/bash
Now execute the instructions to manually install and configure Grub. On Debian systems, it mostly consists of
You might want to reinstall and configure grub again instead:
aptitude reinstall grub
update-grub # This should be useless as run by aptitude
Note: if you don't have aptitude installed you can safely replace
apt-get in the above instructions.
Once you're done,
unmount all previously mounted directories and reboot. Or, shorter:
I cannot guarantee you that your system will actually start but that's how a manual grub install looks like on a Debian system. Replace of course
sdb with your actual disk devices. I have assumed you aren't using LVM, too.
Im Installing Debian on an Old 650Mhz and 200MB RAM machine.
EDIT: Further re-reading your initial post, I recalled that hard drives appeared not as
/dev/sda on older systems but
/dev/hda — does your machine have an IDE drive? So there might be circumstances your hard drive simply is not found by the installer. Or the BIOS...!
I haven't touched any really old system for... well, can't remember! So I have little idea how it turns out when you whack in a fairly recent distribution on hardware that's that old. I remember there was a transition period of time IDE and SATA drives appeared alike but it was a very short period. Maybe that's a hint. Or not.
Also, as a side note be sure to flag the partition that actually boots your system, i.e. the one that the boot loader is installed. That one is called the
boot partition. Of course, if you installed the boot loader on the root partition, then that's the one you must flag as bootable, otherwise it's usually
/boot, hence the name.
If you installed the boot loader on the hard drive (e.g.
/dev/hda, without the partition ID), I don't think you need to flag any partition at all... at least fro my experience with SATA drives and recent machines.
There are cases
/ are the same partition. However I believe however modern installers do generally prepare any minimal system with at least one distinct partition for the boot code/loader.