I tried to make a dual boot setup on my computer. Already had windows 7 installed on one hard drive, then tried to install ubuntu on part of another hard drive. When i turn my computer on windows7 always boots, there is no option to select which os to boot regardless of the order i put the hard drives to boot from in the bios this always happens. If I remove the hard drive with windows on it instead of booting ubuntu it just says there is an error - windows can't boot because something is missing. After installing ubuntu it said everything was fine. Something else which may help: originaly i had kubuntu installed before windows but when i insstalled windows 7 i could no longer get to it and just stopped uing it. How can I stop this from happening so that I can boot into Ubuntu?
What's happened is that Windows 7 has overridden Grub (the Linux boot loader) with its own bootloader. This is fixable, it just takes a little bit of work. Here's how to fix it. You'll need an Ubuntu 10.10 live cd.
Boot into the live session Open a terminal (Applications > Accessories > Terminal) and become root by running
sudo su -
Next you'll need to inspect your disk and look at the partitioning. Run
You'll need to do a little bit of detective work, but you want to identify the Ubuntu root partition. you will get output that looks like this
Device Boot Start End Blocks Id System /dev/sda1 * 1 18663 149903360 83 Linux /dev/sda2 18663 19458 6384641 5 Extended /dev/sda5 18663 19458 6384640 82 Linux swap / Solaris
With another for your windows setup. The /dev/sda1 line, and the numbers will probably be different, but you want to find the one that is listed as System: Linux.
Now you'll mount that, and install grub.
mount /dev/sda1 /mnt grub-install --root-directory=/mnt/ /dev/sd1
replacing /dev/sda1 with what yours said.
That should be it, reboot and you should be able to boot Ubuntu and Windows.
You need to install grub on the correct hard drive (the drive that boots first). To find detailed info on how to do it: here
If you don't feel confident installing GRUB again using the install cd i recommend downloading and installing Easy BCD for Win7.
It should be able to recognize all operating systems installed and allow you to easily decide the boot order