bootloader in windows 7

Umm, the Windows 7 bootloader is present in Windows 7 and the Windows 8 bootloader is present in Windows 8. So I don't understand your question.

Each version of Windows installs its own bootloader. If you multi-boot different versions of Windows on your machine, it's important to install them from oldest version to newest because newer bootloaders support older OSes but not vice-versa.

Could you make it a little clearer what you want to know?

EDIT: For massive amounts of information, see
http://www.sevenforums.com/
http://www.eightforums.com/