Fortunately, I’ve discovered a little gem of a utility: DesktopOK. This nifty bit of freeware lets you save and restore icon layouts. Set your icons the way you like them, save the layout, then just restore it later when the need arises.
And you’re not limited to one layout: You can save as many as you want, which is great if you want different layouts for use with, say, your laptop with and without an external monitor.
DesktopOK works with Windows XP and Vista. Haven’t tested it with Windows 7 yet, so let me know (in the comments) if you have.