Make Hard Drive appear as Bootcamp for Parallels
A late reply to this, hopefully you have already found a solution.
Just because I was having a similar issue getting my Windows install on an external SSD to recognise the internal SATA drive in the iMac. For me it was because the AHCI/SATA controller would fail with an error 10 and after much testing with driver updates etc I believe I found a solution.

The problem for seems to be do with how the drive is formatted / partition table as whenever I do so with Disk Utility then Windows fails to load it. However this was not the case when the bootcamp partition was on the internal drive or even when Windows booted from the external drive but still had a Windows partition on the internal one.

As Windows setup can see the internal drive during installation then you could use this format a partition created as FAT32 in OS X, which is pretty much what Bootcamp creates. That or just use the Bootcamp Assistant to create the partition and instead of going through with installing Windows stop after the part where you format the destination as NTFS.