This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
In the nbproject (short for "NetBeans Project") folder NetBeans saves some configuration-stuff for profiling-settings, build-scripts, etc. So you shouldn't remove it if you want to continue NetBeans as your IDE. (Even though it's good practice to have a build script which is independent from your IDE)