To boot to the Windows 7 drive you need 3 things.
The partition with the boot files has to be active.
Put the boot files in that active partition, if not already there.
and the active partition has to be the first one the system encounters during boot.
If you only have one drive now, the last requirement is taken care of. So you need to set the Win 7 partition active and put the boot files there.
To set the partition active, use a third party bootable partition utility, or boot to the install/repair media and use Diskpart.
To place the boot files, do a startup repair a couple of times or use bcdboot.
So, boot to the Install DVD and go to the command prompt in the Repair section.
Type these commands, one at a time, followed by enter and wait for a response:
Diskpart
list disk
select disk 0 <--use Win 7 drive, probably 0
list partition
select partition 1 <--Use Win 7 partition number
active <-- Sets partition active
exit
exit
Now go to the startup repair section and run it 2 or 3 times, as was suggested.