I am here again. Thanks for the answers. I didn't have time in the last few weeks to play with my little T1, so I just read books on it.
But the problem is still there for me. I can't see any partitions when I am connecting the reader in recovery mode via usb. So I can't reformat the data partiton, too. I don' understand why... I saw them at the first time when I did this repartitioning.