read my signature on how to use grub.
please provide as much detail for your error in post 5 pls.
at first glance....you friends here have tried to help you with the grub-install command but you are better off with the command installs using either a live cd or your distro go into recovery mode and mount your hard drive that contains the /boot
root (hdX,y).....read my signature what that means
if you have linux /boot as 3rd partition then root (hd0,2)....and you know you have success because just before quit you will see grub saying it is installing and finds your other grub booting files and succeeds.
the above works better with a live cd.....let me know if you need help if you have no live cd.