Um... excuse me, but I live in Minnesota. Our Winters are rather chilly and yes, I actually HAVE thought of this. I've actually thought of piping in cold outside air to act as coolant for a PC. It would work fine, so long as you take into account the two factors I listed above.
Now as it happens, I live on the top floor of an old apartment building. During the Winter, the heat from the lower apartments tends to collect in my apartment, making it extremely warm (and not healthy for my computers). There are times when it's necessary to crack a window just to keep my systems from overheating. My HTPC does have a temperature gauge and at times, cracking the window does lower the CPU temp by about 10 degrees Fahrenheit while still being a comfortable living space, but I'm not going to throw open all my windows and wander around my apartment wearing a parka.
What you're thinking simply is not feasible.
-Wolf sends