reinstall grub onto MBR after windows installed on a dual boot system

It's not the first time CSDN blog lost my work.. I have to come here to post my technical articles. sorry for the inconvience for myself.

Here are the steps
- find a bootable linux CD
- get a terminal and type

sudo grub

- now find where's grub installed

find /boot/grub/stage1

- tell grub where is the grub root installed (for example, first hard disk, first sector) and set it up on MBR

root (hd0,0)
setup (hd0)

Make sure that /boot/grub/menu.lst is there and unaffected when you install windows. Or you'll have to make change to that file.