..lets say (I'll use the firefox history example again) that the history file is deleted on XP, I reboot the computer, find the new history file, go to Previous Versions tab and look for the previous one. Its not going to be there, is it? Because the snapshots in XP don't survive reboots? If I checked before I rebooted, it probably would have been there though.
If the file is on a local disk, no, you won't have a 'Previous version' of it. (You may be able to finagle the system to provide one, though, but then we're into special cases.) In this case, you had to look for local backups.
In a typical business environment, My Documents (at least) was placed on a file server to allow for centralized backups. In that case (assuming the file server is WS2003) you probably had 'Previous Versions'. (Assuming default placement of files in the users profile directory.)
..lets say (I'll use the firefox history example again) that the history file is deleted on XP, I reboot the computer, find the new history file, go to Previous Versions tab and look for the previous one. Its not going to be there, is it? Because the snapshots in XP don't survive reboots? If I checked before I rebooted, it probably would have been there though.
That's my current (but changing every second) understanding of it, is that how you see it as well?
No, very likely on a "normal" (not "corporate", not connected to a 2003 server) you wouldn't even have the "previous versions" tab, and, unless you manually created/added something that would trigger the creation of a snapshot, no snapshot would be created (not even temporary, before reboot).
jaclaz