I can't tell you which boot loader you have, but if it's lilo, then download tom's rtbt disk, image a floppy with it, and use it to reinstall lilo.
http://www.toms.net/rb/
If it's grub, then download 'Recovery Is possible' (RIP) from here, and use it (after chrooting into your old system) to reinstall grub.
http://www.tux.org/pub/people/kent-r...looplinux/rip/