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#11
Once Win7 is installed and there's no chance it will place it's boot files elsewhere you can reconnect the other HD in a DISK position lower than Disk0 which should be for the SSD unless it cannot otherwise be.
You can then access your data from Win7, even boot the other drive if needed by tapping the one-time BIOS Boot Menu key. When time comes delete Win7 partition to correctly uninstall the OS after marking it Inactive. To move the User data files off first for linking from WIn7 as suggested earlier, shrink space to create a new partition to copy them into. But to get it cleanest of all move the data off external to wipe the old HDD with Diskpart Clean Command then repartition in Disk Mgmt.