Dual Boot Ubuntu/Vista GRUB Error 21

Jon - Sep 22, 2008 at 11:11 AM
 ankur - Nov 12, 2009 at 06:12 AM
Ok, I have Vista and Ubuntu dual booted, on separate hdds. I had just finished beating Crysis: Warhead, an awesome game by the way, for some reason my computer bsods. I reboot and when it restarts I get a GRUB21 error. So, since I'm sorta new to Linux, from what I know, this means that the Linux mbr can't be found right? To fix which, I assume I need to throw the Linux cd in and repair....correct? I guess it's not all bad b/c I had planned on reformatting anyway, and all my important info is on my data drive which is separate from both OS drives. I'll try this, but since I'm new I didn't know if it would work, and what others had to say about it. Thanks.

6 replies

open live cd
open terminal

sudo grub
find /boot/grub/stage1 or find /grub/stage1
Thanks a lot coolboi007! It works perfectly.
hmm when i do the find command, it returns "not found" is that bad? I think so. The system used to work fine, then after I hooked up a usb drive, it started returning the error 21.
Thank you for your post!! Your suggestion using the 'find' command -didn't think of that. THANKS.e
How did you dual boot Vista with Ubuntu on 2 hdds in the first place? I'm trying to do it with XP and I'm not getting any luck. Please email me the response.
tutorial here (works with xp too i think):
Tom6 Posts 142 Registration date Friday July 31, 2009 Status Member Last seen August 7, 2009 16
Aug 1, 2009 at 10:46 AM
I am guessing that you are new to linux and might appreciate a few other links


Also to get to forums specific to your particular version of linux try navigating through from this site

Good luck and regards from
Tom :)
Tom6 Posts 142 Registration date Friday July 31, 2009 Status Member Last seen August 7, 2009 16
Aug 1, 2009 at 11:19 AM
Most versions of linux (distros) make it easy to open a command-line, just look for the icon that looks like a monitor/tele with a ">" mark in it. That's the usual icon most distros use and it's usually on one of the taskbars, which we call panels for fear of being sued by microsquish ;) In Ubuntu it's quite tough tho, go up to the top taskbar/panel and click on

Applications - Accessories - Terminal

Again we have called it a "terminal console" since about 1981 or perhaps even before but those smart microsquish people called it a "command window" so we can't use that term now ;( lol

Anyway, good luck and regards again from
Tom :)
even after i installed the grub nd grub is workin perfetly fine its show both option ubuntu and xp..but when i click to ubuntu is shows "cannnot mount selected partition press any key to continue" and when i press it again goes to os menu .plzz help i hav lots of data which is in ubuntu...

ankur > ankur
Nov 12, 2009 at 06:12 AM
it shows error 17:cannot mount selected partition

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Tom6 Posts 142 Registration date Friday July 31, 2009 Status Member Last seen August 7, 2009 16
Aug 1, 2009 at 11:12 AM
Ooops, sorry i am new here! I meant that last post to go into a different thread! Ah well i guess it's ok in here? Sorry chaps.

Anyway here goes. I am guessing that everyone already in here can skip to the end as it looks like you already know most of this but here goes for any noobs stumbling in (welcome in any noobs btw ;) )

When you download Ubuntu from
then make a cd of it by double-clicking on the iso file, this guide might help
i tend to find the cheapest "write once" cds that you can only get in blocks of 10 or more are better for this than more expensive cds and dvds tend to be really rubbish for this. Anyway once you have the cd then boot up from it to the menu with "Try Ubuntu without changes to this machine", if you don't get that menu then this guide might help
Choosing the "Try Ubuntu ... " option should get you to a working desktop which we call a "LiveCd session", if it works ;) Most versions of linux have this feature although they don't all have such a fancy menu. Ubuntu's LiveCd has firefox on the top taskbar and should have worked out your internet connection so having got a LiveCd session working you should be able to surf around and check that Ubuntu is going to work easily on the machine. Once you've done that then a dual-boot is better than wiping off an existing working OS, even if that is Windows ;)

Right, not so great for putting Ubuntu on a separate drive? So when you get to the "Partitioning Section" of the installer choose the very bottom of the 3 options. It's not easy to spot because it looks quite different from the first 2 options and doesn't have a nice graphic of the hard-drives. Ok so the bottom option should be "Manual Partitioning" and when you choose it the installer rescans your drives which is a bit scary if you're not expecting it. On the new screen edit your partitions to set the "Mount Point" of the OS partition for Ubuntu to "/" as the / shows the root of the folder-structure for linux. This only needs to be about 10Gb at most, half that if you know what you're doing ;) Then edit the partition you want to use for data&settings and set it's "Mount Point" to "/home", notice the "/" at the beginning of "/home"? ;) So hopefully now you have partitions setup something like this

sdb1 Primary Partition 5Gb(ish) 'file-system' = linux-swap No "Mount Point"
sdb2 Primary Partition 10Gb(ish) file-system = ext3 & Mount Point = /
sdb3 Primary Partition Lots Gb, file-system = ext3 & Mount Point = /home

The beauty of linux is that it's gives such a huge freedom OF choice. If your ram is over 2Gb then put the linux-swap at the end of the drive because read/writes are slower at the end and you don't really need swap except if you sleep/hibernate or suspend your machine - in which case
swap = ram or more
or else you may be in trouble later. Note that having swap larger than 2xRam is a waste

Anyway after installing Ubuntu you might find you can resize the sdb2 in the example right down to 5Gb quite safely. I only made it 10Gb in case you forgot to make a separate partition for /home or had trouble setting it up in the installer ;) heheheheh. A failsafe ;)

People often like Windows because it gives such great freedom FROM choice but that's one of the reasons viruses like it too
I quite like it because it can be relied on to go wrong and fixing Windows pays well :)
Anyway welcome to the wonderful world of linux
Regards from
Tom ;)
I have the same problem. How could i open terminal window? Is it grafical boot menu? Thanks a lot,