If the link by Hermitt does not work, try this more complete procedure:
Follow these instructions to get to a command prompt (and backup your files if needed).
You could try an "Automatic Startup Repair" (run it 3 times to make sure), if that does not work, get to the command prompt, and run the following commands to make a new bootloader:
Follow the tutorial to check the letters of your drives (C:\, D:\ etc.) from Notepad's "Open File" dialog. They may be different in an environment like this: for instance your recovery partition may be labeled "C:", and your Windows 7 may be labeled "D:", although this is rather unusual.
Then mark your Windows 7 partition as active. Use the following commands:
(you are now inside DISKPART>)
select disk 0 (select the hard drive with Windows 7)
select partition 1 (select the partition with your Windows 7 installation)
You can now try to restart. If it is not fixed, try to repair your bootloader. Change directory to E:\boot, where E: is your Windows 7 install DVD (check the drive letter):
cd /d E:\
Run the following command, where C: is your System partition (check the drive letter):
bootsect.exe /nt60 C:
Then restart your computer.