Without an internet connection I don't see how you could download another distro to perform a fresh installation to correct the problem.
If you have a usb or CD of Knoppix or g-parted you can wipe those partitions away completely.
The only other way that I know of is to use DBAN to wipe the disc.
OR> use the dd command to wipe the whole drive but that will take a while.
Here's the instructions for using the dd command.
Wiping the entire diskEdit
This will overwrite all partitions,
master boot records, and data. Use the sudo command as well (sudo dd...)
- Filling the disk with all zeros (This may take a while, as it is making every bit of data 0) :dd if=/dev/zero of=/dev/sdX bs=1M *replace X with the target drive letter.
- If you are wiping your hard drive for security, you should populate it with random data rather than zeros (This is going to take even longer than the first example.) :dd if=/dev/urandom of=/dev/sdX bs=1M *replace X with the target drive letter.
The reason one should fill with urandom in case of required security is explained here:
[1]
Important Note: You need to replace
sdX with the device name you want to overwrite.
sda is usually the first hard drive, the second drive would be
sdb
and so on. Use for example gparted to find the correct drive. If you
replace the device name, you can also wipe USB sticks and other
peripherals.
Wiping the Master boot record (MBR)Edit
If you messed up your
master boot record (MBR) you can wipe it using this command :
dd if=/dev/zero of=/dev/hdX bs=446 count=1 *replace X with the target drive letter.
Wiping partitionsEdit
You can wipe a partition using the same method than for the whole
disk. Just replace the device identifier. If /dev/sda is the whole disk,
then (on Linux, because the naming scheme vary from one Linux to
another) /dev/sda3 is the third partition on the disk.
- Filling the second partition on the /dev/sda disk with all zeros :dd if=/dev/zero of=/dev/sdX2 bs=1M *replace X with the target drive letter.
- Filling the third partition with random data :dd if=/dev/urandom of=/dev/sdX3 bs=1M *replace X with the target drive letter