The PC Doctor has excellent advice on what to do when you PC locks up. It’s an excellent eight-point checklist, which is well worth reading and remembering right now, when your computer is working just fine. When you’re confronted with a mysterious lock-up, it helps to fall back on training like this. You might even want to print out the advice!
Oh, and he echoes one of my favorite pieces of advice in the “What I don’t do” section of the same piece: Don’t just start randomly pounding on the keyboard in the hopes that you’ll hit the magic key. If Windows is temporarily locked by a process that is refusing to give up control, you’ll fill the keyboard buffer with those random keystrokes, which will be executed in horribly annoying fashion when the misbehaving app finally surrenders control.
Ed Bott 
Hey, I’m good because I do those things and don’t do the others! Where I laugh is when people blame Microsoft Word, even if it’s not running.