Rang Toshiba Technical Support and while they could not confirm that the constallaton.2 1 TB 2.5 inch HDD would work with the Qosmio X500, They did confirm that the Qosmio wouldwork with a 1 TB HDD. So there is no restriction via BIOS.
Usually it should not be a problem using 1TB HDD. The SATA controller will support this and if there is no restriction in BIOS, you should be able to get it working…
Feedback would be appreciated..