I am currently using Ubuntu 11.10. My HDD has been frequently used for more than 5 years now. When I try to use the sudo command, or execute a command as root, I receive a message stating that the filesystem is read-only. For example, when I try to run sudo apt-get install gnome-tweak-tool, I receive the following output:

sudo: Can't ipen /var/lib/sudo/aaron/0: Read-only file system

W: Not using locking for read only lock file /var/lib/dpkg/lock

E: Unable to write to /var/cache/apt/

E: The package lists or status file could not be parsed or opened

I have heard that Ubuntu will make the filesystem read only because of disk errors. After checking my hard drive with Disk Utility, I discovered that it has 7 bad sectors. Disk Utility also warned about imminent disk failure. Is this kind of thing normal, and can/should I make the filesystem writeable again? Or should I simply replace my hard drive?