Ways to start certain line with a word when it match a certain word?

[cyberray]

Hi guys,i need to put a certain word infront of 7 sentence after it match a certain word,for example

root:
hi how are u
i am fine
do u knw me
nope i dont
nvm
now
u knw me

what i wanted is:

root:
root :hi how are u
root:i am fine
root:do u knw me
root:nope i dont
root:nvm
root:now
root:u knw me

ya is somehw like this,which mean when it match root,the next 7 sentences will need to start with "root:",can sed or awk do this?pls help out,thanks alot!!

[radoulov]

awk 'c&&c--{print "root:",$0;next};/root/{c=7}1' filename

[cyberray]

hi thanks alot!i find out another way to do it le..thanks for your solution though