boot failed after Fedora 16 yum update

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http://forums.fedoraforum.org – i did yum update yesterday. after that when start my system boot failed. Code: Error : kernel panic - not syncing VFS unable to mount root FS on unknown block(0,0)           PID 1 comm swapper not tainted I am able to boot system in recovery mode. But in recovery mode i need to press Ctrl-D to come out of shell What i want is previous state of my system. Can someone please help how to restore the same state again ?:( (HowTos)