What happend was:

- windows 7 was installed and present in a big HD of 500gb that was not partitioned.
- I started installing Ubuntu. I choose to extract 2gb from the 500gb for swap, but during the partitioning something went wrong and the system crashed.
- I re-booted and the partition was now labeled as unknown.
- I continued the installation of Ubuntu partitioning this unknown partition in 2gb swap and 100gb for Ubuntu.

I don't remember whether when partitioning I chose swap and Ubuntu to go to the end of the unknown partition or not (but I think I did).