After much experimentation I was able to get my Windows 7 (64-bit) system to boot both natively and within the VirtualBox VM system (4.1). The key was recognizing that although all the drives attached to the 3Ware controller are SATA, the interface presented to the OS is SCSI. On the VirtualBox side I selected SCSI (LsiLogic) for the Windows7.vmdk .
While windows was booted natively I used regedit to force loading of the LSI SCSI driver at boot time as well as the 3Ware driver.
At HKEY_LOCAL_MACHINE->SYSTEM->CurrentControlSet->services->LSI_SCSI change "Start" to 0:
Start REG_DWORD 0x00000000 (0)
This cured the 0x0000007b error I was getting previously.