1) I have all drivers from the original vendors. I’m just that darn cool.
2) I installed it to play an old game with a version checker. I then moved the game (safely, BTW, which is trickier than it sounds) to a Vista box for a friend. I don’t even remeber what game it is at this point, but regardless…
3) You don’t need to install NT 4 to actually use the upgrade edition.
4) While I don’t recomend an inexperienced person running an upgrade, I’ve run upgrades that have been every bit as stable and fast as the full versions. On Windows Vista Ultimte, no less.