Restore GRUB boot loader after other OS has been installed

After updating Windows XP to Windows 7 Grub-loader has been lost. I can't work without Linux. And I found this solution:

At first Load from live-cd

grub

Let's know where os install

find /boot/menu/menu.lst

Output will be like this

(hd0,3)

Tell grub where its files

root (hd0,3)

And install it

setup (hd0)
quit
reboot

After rebooting we can see the GRUB-menu.