This has happened to me and my daughter a couple times, mostly on CD drives (the result of repeat read attempts on a damaged CD). The advice above about removing and letting Windows reinstall the device is sound (haven't tried the other method), although IIRC I've had to remove the IDE 'Controller' itself in order to get Windows' attention. I did have one hard drive do it (a factory replacement of a warranted WD 160-gig), but by that time I had already bought a new, larger drive that required a different driver. So to this day I don't know if the problem happened when my original drive crashed, or if the refurbbed 160 WD sent was faulty. But I would say that if your drive repeatedly goes into PIO mode, it's time for a new one.
