I have recently installed Windows 7 64 bit on a new SSD using UEFI boot and GPT. The system worked fine. After adding my old system HD to the system (that uses MBR), Windows will no longer boot correctly: When booting from the SSD, the normal boot screen appears and Windows tells me that it is loading files. Then the boot screen disappears and I am in an EFI shell, unable to boot. When I unplug the old HD, Windows boots again without complaints.
Can I somehow boot with this configuration without formating my old hard disk first?
I have an MSI Z77-G65A board. It is configured for UEFI boot, booting from the SSD. Both drives are set as independent HDs (no accidently activated RAID). The SSD is connected to a SATA-6G port and the old drive to a SATA-3G port.