When I try to install ubuntu 10.10 from the official livedisc I got in the mail, when I get to the "Allocate Disk Space" step I cannot get it to work. I shrank my win7 partition so I have unallocated space, then I tried using the space while it is formatted in NTFS, but the partitions will not show up in the box. /dev/sda is selected under boot loader, and I can't select anything else, but the partition box is blank so when I click "install ubuntu" it just says: "No root file system is defined. Please correct this from the partitioning menu."

-I am trying to dual-boot win7 and ubuntu, but I was never asked in the install process whether I would like to install just ubuntu or dual-boot?