Boy oh boy...I think I stepped in a pile of it this time. My Linux Mint Olivia 15 was working just fine. Was that good enough for me? No. I HAD to get Linux 16 Petra. I followed the Apt-get terminal commands. Now my computer starts like it is going to launch Mint with the little green "L" in the screen center...then it goes to all black screen. That's it; it just sets there. I have attempted numerous times the restore in safe mode by holding the shift key after the BIOS boot...and I have clicked all the possibilities including fixing broken program packages. Still nothing. Is there any way I can REVERSE adding Petra and restore to my previous Olivia? My computer is booting only to LINUX (I removed Windows a while back). By the way, I am writing this on a lightning fast Dell desktop 700 MHZ system. So I can't do too much with screen captures on my DOA Linux computer I am afraid. Hope there's someone out there who can help.