How to disable raid after I connect disk to computer

Hi,

how can I connect my disk from raid to computer ?

I have x-raid, I had there 2x1TB disk.
Now I bought 2x2TB disks and I hoped that my x-raid (expandable) will just expand to 2TB :-). A unpluged first, put in 2TB and wait for mirroring, then I did same with second 1TB disk but now I have 2TB disks in raid, but there is still just 1TB free place.

So, I can format it and create new raid, no problem. But I am lazy copy all data from nas to COMPUTER, so I would like be able disable raid on that old 1TB disk, which in now on the table, not in nas :-).
Can I do it with some SW for windows ? you know... I will connect it to sata, run windows and then use tools to disable raid so I will have accessable all data and I dont need copy them from nas to computer.

How to this ?
(or how expand my NAS, I have there 2.2TB disk, all is workiing ok but there is just 1TB place)