Ok, it was late last night and you know what happens when running sudo at that time...disaster.
I ran
sudo dd if=/dev/zero of=/dev/sdb bs=8k count=10k
on two of my harddrives, both containing my data. (I was testing write speeds).
First drive had ext4(ubuntu) partition and ntfs partition (latest is important to me). Second drive had ntfs or fat32 (XP installed) and ntfs also with data(important). So is there any hope? I have read that dd starts writing from first block. What is there? Partition tables?
fdisk -l says:
Disk /dev/sdb: 640.1 GB, 640135028736 bytes
255 heads, 63 sectors/track, 77825 cylinders, total 1250263728 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00000000
Disk /dev/sdb doesn't contain a valid partition table
