Boot from rescue DVD and see if you can mount the root volume. It should end up at
If you can't do that it means the partition table may be corrupted. Check with:
Code:
parted /dev/sda print
If it is busted, try rewriting the table but not initializing the partitions using your carefully made records.
If you don't have carefully made records (the normal case) parted has a rescue command to try to find your partitions. Post back here if you get stuck.
Note: Most important thing in rescuing a disk is to sit on your hands until you know
what's wrong. Don't just start trying things. And make sure you keep a record of
what you do and what happens.