Shrinking ubuntu partition.

[st_itty]

I have a 160 GB hdd which dual boots vista and Ubuntu. I have 2 main partitions 110 GB ntfs with vista on it and a 30 GB ext3 one with Ubuntu. I want to shrink both the partitions and create a new partition which would be my common data drive. I'm planning to shrink the Ubuntu partition to 10GB currently its only using around 5 gigs. My question is 10 GB enough for ubuntu and can I shrink this 30GB partition to 10GB. I tried to do it in GParted but all options are disabled(I'm guessing this is because that partition is mounted).
Thanks.

[mikewhatever]

You should be able to shrink it using Gparted Live cd. The sizes are entirely up to you.