Tricky Cat-5 Wiring

[Dave Smith]

I know this is somewhat off topic, but then again, what isn't on Plug?

I live in a 3-story house with all three floors finished. The house is  
about 5 years old. Some of the rooms have cat-5 wiring, but others  
don't. One such room is the office on the middle story, where I want  
to run some cat-5 (there are so many Wi-Fi networks in the vicinity  
that my bandwidth stinks). I have cat-5 in the attic, which originated  
in the basement, that runs to other rooms on the same floor. So my  
question: Is it possible to run a cable into a room on the middle  
floor without totally trashing the drywall? I just don't see it, and  
my Google fu has apparently waned.

Thanks in advance.

--Dave