How many partitions and drives are you showing. XP sometimes messes up and gets confused with drive letters over "F" , "G", "H". The work around on this is to change your optical drives to a higher letter designation such as "X","Y".or"Z". This particular problem really shows up with removable flash drives but since you had to reformat... windows sees your other hdd as a removable drive and thus was unable to assign a drive letter to it.
This is showing up more and more now with bigger drives and more partitions and the likes.