Courtesy of fellow forum member Genkaku
there *might* be a last ditch effort to get this to work.
Boot the computer, get to the GRUB menu:
1. Do you have a System Upgrade (fedup) option? If yes, choose that and see what happens.
2. If you don't, you'll have to use an existing entry as a template. Doesn't matter which one, select it with arrows, and type e to edit it.
3. Tricky. I can't give you the correct entry from scratch. You have to look at a before and after, and figure out how to edit your entry. The two lines you're going to change start with linux, and initrd.
linux /boot/vmlinuz-3.7.4-204.fc18.x86_64 root=UUID=b60a1745-f85f-4e85-b3ca-cc1166ff255f ro rd.md=0 rd.lvm=0 rd.dm=0 rd.luks=0 vconsole.keymap=us rhgb quiet
linux /boot/vmlinuz-fedup root=UUID=b60a1745-f85f-4e85-b3ca-cc1166ff255f ro rd.md=0 rd.lvm=0 rd.dm=0 rd.luks=0 vconsole.keymap=us rhgb quiet upgrade systemd.unit=system-upgrade.target plymouth.splash=fedup
The basic gist is that I only changed:
1. vmlinuz-3.7.4xxxxx to vmlinuz-fedup
2. added upgrade systemd.unit=system-upgrade.target plymouth.splash=fedup
I did NOT change the root=UUID, or anything else. Your entry may or may not begin with /boot. Leave it the way it is and just change the ending on vmlinuz so that ends with -fedup. That's it. Then add on those three items to the end of your existing line.
Next change is easy, the initrd line:
F10 to boot with these changes. Hypothetically, if you still have all the files, it will start the updating from scratch. ??? But just saying, I think that it will get pissed not finding old F17 packages which have been upgraded to F18. It's not going to be smart enough, probably to either overwrite them, or skip them. But I don't know. You'll just have to try it and see, but I think it may not work. But it's the only thing I can think of at the moment.
NOTE!! The first code block above scrolls way off to the right, the code doesn't wrap. So you have to make sure you get your mouse arrow in the code region and scroll to the right to see all the code.