1) You can pop the "W" key off of your keyboard, and clean it or replace the rubber foot if necessary.
Use a Q-Tip, soaked with Isopropyl Alcohol, that should eliminate any grime that's causing your W key to stick.
2) Your "W" Likely doesn't work because it's either got too much crap gummed inside of it, or the rubber foot (it's a piece of rubber between the plastic "W" key, and the circuit board inside your computer) was disloged. In either case, as it doesn't work either way - you might as well pop it off and find out what's going on =)
