Here's a tip I wish I'd known about a couple days ago. I was moving a lot of font files around and I didn't want to overwrite newer font files with older ones. In my case, I was working with Postscript fonts, which have incredibly cryptic names such as bdbc____.pfb. (That's Bodoni Bold Condensed, in case you're wondering.)
There was a huge list of files that I was working with and I didn't bother trying to figure out which files were already there. (Again I was faced with the cryptic file name problem; they all look the same to me.) Because I didn't want to replace files when I was copying, I had to click the No button every time Windows XP asked me if I wanted to replace a file. (No, no, no!) What I wished I'd had was a little "No to All" button, but there wasn't one.
For some reason, Windows has a Yes to All button, but not a No to All button in its little error dialog box. You might also run across this situation if you copy a bunch of files and Windows gets "stuck" on an error, such as encountering a read-only file. After you fix the problem, you need to start the copy process all over again and you don't want to figure out where it left off, so you just copy all the files. But you don't want it to replace the files that were copied the first time, since they're already there. Why is there no "No to All" button? I have no idea.
But there is an undocumented keyboard shortcut. So without further ado, here's the o-so-cool "No to All" tip. When you click the No button, hold down the Shift key at the same time. To Windows, that combination means "No to All." Who would have thought it!
Now all I have to do is actually remember that tip the next time I have a big file copying experience.