Networking problem

I had a problem with one of my computers and i had to
redo the whole c drive but i had a network hooked through
my router. Well I was able to use my printer on this
computer from other computers but know it won't work. I
can use the internet on all of them but i can't share
files and share the printer, even after making them able
to share. I don't know why know it won't work. Please
help someone!

Craig