Disk Utility Help Needed.

hey mate, its actually pretty simple..... well unless they changed things with lion... everything that should be simple isn't... but anyway

you typically can't unmount the os, and you can never delete a mounted partition... because you are using it. there are two ways around this, one is to use an osx install cd, then use the disk utility from there, because you are running off the CD, NOT the hd.

If you have a bootable backup, you can also boot from the backup, and use the disk utility again on the internal drive.

 

So you are booted off of an external USB stick with the Lion Recovery HD on it or Lion Installer? You will need to startup using this - not the internal drive.

I'm not sure exactly why you would get the error (unless, as the previous post said, you are booted off the internal drive), but if you want to erase the entire drive, you can set it up with a single new partition. In Disk Utility, select the drive itself (not a partition), then click on the Partiton tab. In the layout menu, select "1 Partition", format "Mac OS Extended (journaled)". Then, click Apply. This will erase all the data on the drive.

Is your USB drive just the Recovery HD partiton, or is it a full install? If the former, you will be downloading Lion, so expect the install to take a bit of time.

I'm not clear on how you recover iLife, but either it will be part of the recovery install, or you will be able to download it from the Mac App Store. I just haven't read of exactly what the procedure for that is.

 

If you have your reinstall media, then I'm guessing the steps below are what your looking for?