This is not something that happens particularly often, but when it does, it can be extremely frustrating. Every once in a while, I may be browsing the web, playing Doom, RollerCoaster Tycoon 3, or doing something else on my Windows 98 machine, and suddenly, the shell stops responding and everything becomes unusably slow. Most of the time, I can do the three-finger salute, kill every open application and Explorer, and the desktop respawns, and I can go back to what I was doing. However, sometimes the system becomes so unresponsive that it completely locks up. The screen becomes a still image,