Did you run Startup Repair 3 separate times with reboots in between each to try to write the System boot files to the known Windows 7 partition which is marked Active?
If you have done this fully and without shortcut, then try rightclicking on first partition to Modify>Set to Active, click OK, then again highlight Disk1 to Rebuild MBR from Disk tab, Apply. If this fails to start Windows 7 at reboot then again run 3 Startup Repairs to see if it will reestablish it as System partition for the old Windows 7 installation.
If not boot the Windows 7 DVD to Custom Install to the first partition, which will give you access to your old Windows 7 files and allow you to gradually move it over to first partition. If you do this while it is marked Active it may work better than before. I would first use Custom install's Drive Options to delete the first partition (only) then just click Next to let it auto-create and -format and begin install. Clean Install Windows 7
May I ask why you had such a large System partition to begin with? Was there another OS there at one time? Have you had Linux GRUB bootloader on the drive as this can corrupt Windows 7 beyond repair? If not it may be random and reckless changes you made which corrupted Windows 7 beyond repair.