HI, 
I am using using an old 2900XL switch which has IOS V 11 which I tried to update to IOS 12.05. I followed a cisco procedure which instructed me delete the current OS file and then upload the new one with TFTP server. 
I managed to delete the file however seconds after the deletion we had a power cut so now the switch is without an OS and all of the commands that I could need to continure the IOS upgrade are not available. 
What can I do to update my switch now? 
(I am using this switch for my CCNA) 
Thanks