fdisk -l

Disk /dev/hda: 81.9 GB, 81964302336 bytes
240 heads, 63 sectors/track, 10587 cylinders
Units = cylinders of 15120 * 512 = 7741440 bytes

Device Boot Start End Blocks Id System
/dev/hda1 * 597 10586 75524400 7 HPFS/NTFS
/dev/hda2 10587 10587 7560 f W95 Ext'd (LBA)
/dev/hda3 1 596 4505728+ 83 Linux
/dev/hda5 10587 10587 7528+ 82 Linux swap

Partition table entries are not in disk order

I don't see a sda anywhere. Can find info in the info center about sda4 and it says it's vfat.

root@1[knoppix]# fdisk /dev/sda

Unable to open /dev/sda
root@1[knoppix]# sudo fdisk /dev/sda

Unable to open /dev/sda
root@1[knoppix]#

What does it mean when it says it not a valid block device?