GRUB error 21

[alias301]

Ok so I installed Debian to a partition on my External Hard Drive 100GB and 2GB Swap Space.
I had Windows Professional and the installer I got was from Say goodbye to Microsoft. Now.
Now every time I try to boot I get a GRUB 21 error.

Do I need to use Super GRUB and if I do how do I, I am new.


Please Help
-Thanks

[PellRoja]

us a super grub live-cd, start debian and open console, write a comand

sudo apt-get install grub.

if not start debian. diferent solution is repair boot windows. Fixmbr - Repair Master Boot Record, MBRFix for Windows 2000, XP etc., fdisk /mbr, linux LILO damage MBR.

[runtt21]

Grub error 21 means that it is trying to boot a drive or partition that it cant find, did you check to see if your computer could boot from an External Hard Drive before you installed? When you installed where did you install grub to debian's root partition or to the mbr?

You can check your computers boot menu to see if it list you external drive.When you first start up look at the very first screen that comes up it will have the company namelike hp or toshiba and it will have some function keys listed on the bottom , look for the one that says boot menu ,it's different for different companys. On most hp's it is esc , but toshiba is f12 .

Grub is working , it's just set up wrong.

[Jonathan183]

I suspect you have installed grub to the MBR of the internal hard drive but the config files grub is trying to use are on your external hard drive.
You can use SuperGrub to fix the Windows boot so your machine will boot from the internal hard drive without the external hard drive connected ... the option is something like write generic windows code to MBR.

Can you post the output of

sudo fdisk -l

or

su
fdisk -l

so we can see disk partition structure. The l is a small L, you should run the command with your external hard drive connected.

Can you also confirm if your BIOS supports boot from an external hard drive & how the external hard drive is connected to the PC ... is it by USB?