Delete IOS from Flash, boot from new IOS ,TFTP

sh flash

delete flash

confirm y


reload


rommon 1> IP_ADDRESS=x.x.x.x
rommon 2> IP_SUBNET_MASK=x.x.x.x
rommon 3> DEFAULT_GATEWAY=x.x.x.x
rommon 4> TFTP_SERVER=x.x.x.x
rommon 5> TFTP_FILE=1841-i-mz.bin

type 
tftpdnld

and press enter

if everything right the ios will be copied to flash

then 

reset

and you are done