"Not Responding"

Why does Internet Explorer 7, Word 2007, AOL, and just about every other program give me a "Not Responding" message and simply stop working as it turns the screen to white? I can do nothing until it goes away, sometimes a minute, sometimes I have to re-boot. This is on both Vista and Windows 7 OS machines.

 

Different machines or one dual booting? If different I'd suspect malware, especially if they're networked or have shared data/software. It may just be however that you're overworking your computer(s).