What size is the C: drive though - if it's 100MB or thereabouts, then it IS the System drive, as it was created during hte initial install of WIdnows.
By default, on an empty space Windows will create TWO partitions - the SYSTEM RESERVED partition of 100MB, which contains files essential for booting hte system, and the normal WIndows partition.
I would suggest that Sony screwed up their Recovery process - and misaligned the partitions in the registry.
A possible cure for this is to completely re-partition the drive to a single partition, then try the install again.
Somewhere buried in Sony's Support area I suspect there's a KB article on this.... but I can't find it