It's one of those software design decisions that makes you scratch your head and wonder, "What were they thinking?" The "it" in this case is XP's most powerful rebuild/repair option, and yet Microsoft chose to hide it behind seeming dead ends, red herrings, and a recycled interface that makes it hard to find and (at first) somewhat confusing to use.But it's worth exploring because this option lets you completely and nondestructively rebuild, repair, or refresh an existing XP installation while leaving already-installed software alone (no reinstallation needed!). It also leaves user accounts, names, and passwords untouched and takes only a...