Just made the switch from XP to Win7 on my work PC and I noticed something strange.
Some 'undefined' glyphs are missing from system fonts such as "Courier", "Terminal" and "System" (i.e., those that don't have an icon in the "Font" drop-down in "Character Map").
Character codes 0x81, 0x8D, 0x8F, 0x90 and 0x9D had a small square in XP's version of these fonts, but they are empty (zero width) in Win7.
You can 'type' these characters in notepad by holding down the left-hand [Alt] key, typing their four-digits decimal value (respectively, 0129, 0141, 0143, 0144 and 0157) on the numeric keypad and releasing the [Alt] key. In XP you get an empty square, in Win7 you get a zero-width character - nothing is displayed but moving the cursor with the arrows shows that 'something' is there...
Surely, by now, if it was a bug, someone would have noticed it? Why are they gone?
I noticed this because I often write batch files (.bat) for French speaking audience and to simplify accented characters entry (and box drawing characters) I made a file with both DOS characters and the equivalent Windows one. The missing glyphs correspond to the DOS characters ü, ì, Å, É and ¥.