BCD and Grub

Win7 's boot is divided into two parts: MBR program and BCD (Vista formerly known as NTLDR, in fact they are a thing but improved a lot). The MBR program is the first 446 bytes inside the MBR. Windows every time with the official installation disk installation system, will forcibly overwrite the program here for its own MBR program, the MBR program function is very simple, is to start the partition table marked as active partition.
The MBR program then launches the BCD inside the activation partition (BCD has special programs installed in the special location of the partition). BCD implements F8 functionality and formal startup Windows7.

Linux cannot be started here because the MBR first 446 bytes inside the boot program GRUB originally Linux. Win7 installs, overwrites the MBR here Grub program, causes not to start grub, but starts the BCD to start Windows.
But the BCD itself does not support booting Linux directly, so your Linux will not start now. You can only use BCD to start a program that can boot Linux to transition. This kind of software actually does not have much now basic also can choose GRUB.

There are two solutions:
1, repair the GRUB MBR program, this implementation is very simple, as long as the Linux can be started to repair, whether you start a grub for DOS or a Linux LiveCD as long as you enter Linux can be repaired. This fix article is a whole bunch of online.
2. Start GRUB with Win7 BCD to boot to Linux. But BCD is cumbersome to set up, as XP directly modified boot. INI is convenient and intuitive. Grub here is  available with grub for NTLDR, but requires a separate installation method for BCD. You cannot copy XP to modify the boot. ini method.

BCD and Grub