I think you might have formatted the partitions, but not the drive? This would mean that it would find the Master Boot Record still, but then not be able to find the information in the partition about the OS. Which I am guessing has lead to the blank entry.
I haven't reinstalled an XP OS for years, so I could be talking crap. But I would say... format the whole drive and not just delete a partition.
I think you might have formatted the partitions, but not the drive? This would mean that it would find the Master Boot Record still, but then not be able to find the information in the partition about the OS. Which I am guessing has lead to the blank entry.
I haven't reinstalled an XP OS for years, so I could be talking crap. But I would say... format the whole drive and not just delete a partition.