Windows 8 installed its own bootloader (also known as
Master Boot Record), which is currently being used and its own settings. Now, Windows 8 is removed, but since the bootloader is not saved on that partition of HDD, it is still active and being used.
Windows 8 bootloader can no longer find Windows 8 from the HDD, which causes it to run the Startup Repair.
To fix it, you need to go into Windows 7 Recovery Mode (I believe it is done by inserting the DVD and then running it somehow, can't remember right now) and inside there, you need to reinstall Windows 7's master boot record.
A guide with pictures:
http://www.sevenforums.com/tutorials/20864-mbr-restore-windows-7-master-boot-record.html
Had the same thing, when I dualbooted XP and Ubuntu. I removed Ubuntu, but Ubuntu's master boot record called GRUB was still in use. Had to repair XP's MBR, which did the deal. Process is slightly different on Windows 7.