I know there are lots of posts on this already, but I need more help with the one by Kipper, which should work for if I could just find my way to a Recovery screen! Maybe Xubuntu works different. Anyway, I have GRUB blocking my hard drive after I did an installation just to my Sandisk pen drive! So, I have that error when I try to boot my hard disk, doesn't matter whether my CD is in the drive. There is no opportunity to type in anything like "Recovery" at any prompt, just the error message. When I F12 and select my CD to boot into, I get the following menu:
Try Ubuntu...I checked the F4 and F6 options for each of these, and saw nothing on recovery. So, I need more details on how to actually access that screen with recovery options. I've seen such a screen before with a recovery option when I had a dual-boot system (Ubuntu Ibex and Vista), but I only knew how to access it from the hard disk, and GRUB won't let me near it now. The directions I've seen so far aren't helping me, if it makes any difference I'm using 8.10 - please help!
Check CD for defects
Boot from first hard disk