Power failure during upgrade

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http://askubuntu.com – 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. (HowTos)