Restaurar o grub no linux mint 12

oi galera, vamos ao que interessa?

mint@mint ~ $ sudo fdisk -l

Disk /dev/sda: 320.1 GB, 320072933376 bytes
255 heads, 63 sectors/track, 38913 cylinders, total 625142448 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x00007c8c

Device Boot Start End Blocks Id System
/dev/sda1 * 155998206 625141759 234571777 5 Extended
/dev/sda2 206848 155997583 77895368 7 HPFS/NTFS/exFAT
/dev/sda3 2048 204799 101376 82 Linux swap / Solaris
/dev/sda5 155998208 625141759 234571776 83 Linux

Montei a particao sda5, depois tentei instalar o grub, deu isso -

mint@mint ~ $ grub-install /dev/sda
unshare failed: Operation not permitted
grub-probe: error: cannot find a device for /boot (is /dev mounted?).
cp: cannot create regular file `/boot/grub/915resolution.mod': Permission denied
mint@mint ~ $ sudo update-grub
/usr/sbin/grub-probe: error: cannot find a device for / (is /dev mounted?).

O que aconteceu aqui galera? pode ajudar? preciso de uns programas do windows, nao consigo acessar.

Obrigado!!!!!!!!