Here's my analysis of this mystery.
On the Macintosh, when you want to move a window, you can grab any edge with the mouse and move it. On Windows, you must grab the title bar. If you try to grab an edge, the window will be reshaped. When Pete was helping Gena, he tried to widen a window by dragging the right edge. Frustratingly, the whole window moved, rather than resizing as he expected.
On Windows, when a message box pops up, you can hit enter or the space bar to dismiss the message box. On the Mac, space doesn't work. You usually need to click with the mouse. When Pete got alerts, he tried to dismiss them using the space bar, like he's been doing subconsciously for the last six years. The first time, nothing happened. Without even being aware of it, Pete banged the space bar harder, since he thought that the problem must be that the Mac did not register his tapping the space bar. Actually, it did -- but it didn't care! Eventually he used the mouse. Another tiny frustration.
Pete has also learned to use Alt+F4 to close windows. On the Mac, this actually changes the volume. At one point, Pete wanted to click on the Internet Explorer icon on the desktop, which was partially covered by another window. So he hit Alt+F4 to close the window and immediately double-clicked where the icon would have been. The Alt+F4 raised the volume on the computer and didn't close the window, so his double click actually hit the Help button in the toolbar on the window which he wanted closed anyway, which immediately started bringing up a help window, so now, he's got two windows open which he has to close.
Another small frustration. But, boy, does it add up. At the end of the day, Pete is grumpy and angry. When he tries to control things, they don't respond. The space bar and the Alt+F4 key "don't work" -- for all intents and purposes, it's as if those keys were broken. The window disobeys him when he tries to make it wider, playing a little prank where it just moves over instead of widening. Bad window. Even if the whole thing is subconscious, the subtle feeling of being out of control translates into helplessness, which translates into unhappiness. "I like my computer," Pete says. "I have it all set up so that it works exactly the way I like it. But these Macs are clunky and hard to use. It's an exercise in frustration. If Apple had been working on MacOS all these years instead of messing around with Newtons, their operating system wouldn't be such a mess."
Right, Pete. We know better. His feelings come despite the fact that the Macintosh really is quite easy to use -- for Mac users. It's totally arbitrary which key you press to close a window. The Microsoft programmers, who were, presumably, copying the Mac interface, probably thought that they were adding a cool new feature by letting you resize windows by dragging any edge. The MacOS 8.0 programmers probably thought they were adding a cool new feature when they let you move windows by dragging any edge.
