Firstly, thank you for your patience and perseverance

I think that this might be the answer:

Please Note: In order to properly access the full capacity of an ATA interface hard drive or partition larger than 137GB and properly support 48-bit logical block addressing, Windows XP Service Pack 1 or Windows 2000 Service Pack 4 are required. This issue does not affect SCSI hard drives.
Have you updated your Windows, as that seems to be where the problem is? You need Service Pack 4

Cheers