In most of the systems GRUB is now upgraded to 2.0 and with this update the old restore process have also changed now there is no grub command :) available.
If you have lost the Bootloader after a routine reinstall or due to any other reason try the following to restore
Boot Using a Live CD and try the following as root
grub-setup -d /media/XXXXX/boot/grub -m /media/YYYYY/boot/grub/device.map /dev/sda
Where XXXXX represents the root partition and YYYYY represents the partition holding the /boot in case you dont have a seperate partition for /boot then XXXX and YYYY would be be the same. /dev/sda may change depending on the system you are using.
Please note this would erase the current bootloader and install a new one for you if you are unsure of what you are doing do not try this
Once done reboot and you will get the GRUB Menu in case you have lost your other OS from the Menu run a
for more information visit the Documention here.