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You should be able to set which HD is first to boot in BIOS setup. If it will not keep the preferred HD set to boot first then make sure it is plugged into SATA 1 port to be first in order. But sometimes SATA1 OS disk not disk 0 - Windows 7 Help Forums.
Why do you have two Win7 installations? Do you plan to keep both? You need separate licenses for each.
If you plan to keep both then I would make the preferred Win7 OS as Disk0 plugged into SATA port 1, add the other OS's from that one using EasyBCD. If you've already set up EasyBCD from another OS then go there and delete the EasyBCD listings for the other OS's leaving only the native OS listing.
If booting via BIOS is to your liking, then remove the Windows Dual Boot menu by deleting the other listings in EasyBCD than the native one.