Resolved Disk utility-Could not unmount disk

I messed up the partitions on my MBP and now, trying to erase the entire hard drive and restore, when I click erase on the drive, disk utility says Could not unmount the disk even though the two partitions are greyed out on the side bar and can be unmounted manually by clicking unmount but then when i click erase again, i get the same error.

Help would be greatly appreciated!

 

That's what I was going to do, but out Internet connection is slow. I ended up using the snow leopard install cd to reformat the whole drive. It was saying could not unmourned because it wanted to unmount the whole hard drive and it couldnt because the recovery partition is on the drive and was being used. But with the cd, the drive was inactive. Thank you for your input though!