In none of those cases (except maybe the "broken FS" one) do my Windows machines ever bother to assign a letter.
Hey,hey, hey - you lucky boy!
* Win7 asked me often, if it should format my Linux Partition !!! Somewhere in the Win-Jungle I disabled the partition.
Too long ago, don't know, where it was exactly.
* If you just pull the plug of an external drive and you don't inform the OS to "eject" it, you got a valid drive letter - until you try the first time to read or write from/to that drive.
* If a network drive (Samba) does not react, but it was alive at boot times, Win is really insistent. It retries in an endless loop to reconnect. It shows a drive letter and the hourglass but not the directory. Until the end of all days. Or a reboot.
And so on.
Winni