Hm... I'm not sure. Maybe your HDD partition got messed up and grub can't access it and/or there is something physically wrong with your hard drive. Did you play around with the jumpers or conductor cable?
Otherwise, you might need to reformat and reinstall your system
You definitely need a boot floppy to gain some access. Try to get it from a friend or at work, etc. If not, sorry.
If you don't have a floppy and only CD, like I do =P, try the ubcd - Ultimate Boot Cd - http://ubcd.sourceforge.net/.
Haven't checked if they have linux boot disks.