A 250 GB HDD stuck with one 180 GB partition
I have solved the problem now.
All I had to do, is the following, in the right order:

1. Go to Disk Utility &gt; 250.06 GB Hitachi HTblablabla &gt; Partition.
2. Click on "Recovery HD".
3. Click +.
4. Click - on the newly created partition.
5. Click - on the Recovery HD, which suddenly jumped from 650 MB to 62 GB.
6. Resize "Macintosh HD" to 249,72 GB.
7. Click "Apply".


PS: it takes a hell lot of time to finish the process.