|Kind of hard to tell. As you say a "sleep" ought to have more problems getting to work rather than fixing it.|
Might boot to a live cd either barts or even Vista/W7 dvd or Linux to see if the drive works at boot really. Is so then we can assume some issue with hardware.
As to the fix I could only guess a try at the xp "repair" but then you have to reload apps. The only for sure way might be to clean install it but that takes time.
Playing to the angels
Les Paul (1915-2009)