Question: I get this error:

```
Error: unknown filesystem.
grub rescue>

```

I'm not exactly sure what I did. I believe I installed Ubuntu over Windows on my Acer netbook. I then tried to install [Linux Mint](http://en.wikipedia.org/wiki/Linux_Mint), but it wouldn't start installing.

I turned the netbook off and back on. Now I get the error.

I have read a lot of other questions like this, but in my case I cannot boot a CD. If I put a Ubuntu CD or a Linux Mint CD into my external CD/DVD drive and change my BIOS to boot the CD-ROM first, it just gives me the same error screen.

**Update copied from comment dated 2012-05-26 02:54:29Z**

Here are some results from my commands: 

```
grub rescue>ls (hd0) (hd0,msdos5) (hd0,msdos1) 
grub rescue>ls (hd0,msdos5) unknown filesystem 
grub rescue>ls (hd0,msdos1) unknown filesystem 
grub rescue>ls (hd0) unknown filesystem 

```

Answer: 
The following solved the issue for me, I have Windows 7 & Ubuntu 10.04. After running the following commands I don't need to run these every time and am able to boot both the OS normally:

```
set root=(hd0,6)
set prefix=(hd0,6)/boot/grub
insmod normal
normal

```

Now once you boot into Ubuntu, run the following two commands as well:

```
sudo update-grub
sudo grub-install /dev/sda

```

Note: `/dev/sda` is drive where you want your GRUB installed, it can be `/dev/sdb` or something else, but is usually `/dev/sda`

Take into consideration that the `hd0` could be X (0,1,2..) depending on the order of disks and the `6` could be also different, it could be `(hd0,gpt7)`, for example.
Boot your system from the Ubuntu Live CD and try this, it worked wonders for me.

* [Ubuntu Boot Repair Utility](https://help.ubuntu.com/community/Boot-Repair)