During upgrade from 12.04 to 12.10 there was a power failure. computer boots to desktop but without tools and menus to navigate. files that can be open cannot be closed. sidebar menu does not exist. there is no function of the DVD drive, the USB drive nor the internet. Possible to open GRUB but I am not familiar with it's function. Please help.
If you're at a GUI hit ALT-F2 type term and run
do-release-upgrade. If that does not work, use CTRL-ALT-F1 and login to the terminal, then run
do-release-upgrade to reinitiate the upgrade.
If the do-release-upgrade tells you that there is no newer version found or something of the like, then do a manual installation of the UBUNTU-DESKTOP package by typing
sudo apt-get install ubuntu-desktop. That's about all I can think of at the moment that might help you. Good luck.