Here’s part of a screen capture, showing the development of the “file manager” icon in Windows, from the original release to today. (On the site, clicking the icon takes you to another page that has screen captures of the interfaces for the various applications.)
The development of the icon reflects the change from files existing on floppy disks (which needed to be regularly swapped in and out of the early computers) to the metaphor of the file cabinet (presumably more familiar to computer users than the computer).
This page demonstrates how the development of the icon seems to lag behind the technology. How many websites still use what looks like a dot-matrix printer as the icon for “print this page”? The second to last icon in the list above looks like a PC Junior from the late 1980s, with its tiny horizontal cabinet. I guess they wanted enough room to emphasize the screen instead of the CPU, which is a sign that computer users were expected to think of the screen when manipulating their files, not the bits in the CPU (or the papers in the metaphorical file cabinet). The rightmost icon, which shows a flatscreen monitor and a tower case, is for Windows XP Professional; clearly Microsoft expects those users to have cutting edge equipment. The mouse icon has the center scrolling wheel and the keyboard has the curvy wrist rest — both are recognizably Microsoft computer accessories.
My computer, like those of most on our campus, is black — but Microsoft probably isn’t interested in having its icons make users think of Dell. Does any Windows user actually own a flatscreen monitor with a plain white frame?