My Mac running Lion was being slow, so I was decided to reinstall OS X. I don't have any Time Machine backups.
Everything went file, but in the middle of the installation, it got stuck, and later the installation failed without any reason. So, I tried to reboot again, but it said that the reinstallation failed and asked me to reinstall again. I tried to reinstall, but nothing came up.
So I tried to use Disk Utility to erase the startup disk and make a new partition. But, when trying to partition, Disk Utility said that it cannot unmount the disk. In Disk Utility, I found another disk called disk2 and Mac OS X Base System. As far as I know, I didn't see that disk2 in my disk list before.
I tried to unmount it or erase that disk2, but it won't let me. So I tried using Terminal to force unmount that disk, but still it doesn't let me.
Is that disk2 the reason why I cannot partition my main HD? How can I unmount or erase that disk2 Mac OS X Base system ?
I would like to clean install OS X lion again. I already have a boot image on my USB drive. I just cannot start it because the installation fails and something is still running, I guess.
Screenshot of Disk Utility: