XP Pro Explorer Crash

My friend’s system all of the sudden went crazy…
When he opens any Explorer type window (IE, Windows Explorer, Find, etc), and closes them all, he can no longer open anything. He gets the explorer.exe crash. If he keeps just one of those windows open, he can use his system as normally as he does, but once all Explorer windows are closed, he has no choice but to reboot.
He already rpaird his explorer.exe to no avail.
Ideas?