Yes it is a recovery partition, I have the same thing on my Acer 8930G. In fact I had 2 hidden partition 11gig and 4gig. You can keep it if you want or get rid of it. However if like me you plan to dual boot with perhaps a linux distro then it will prove a pain in the butt.
I ended up getting rid of mine. But before I did that I created a recovery disks. And now I guard them with my life...
You should have an option in the windows vista that came with your acer to create this DVDs.
I think that they will actually recreate the hidden partitions if you choose to restore the system to the ACER factory default.