I have Lenovo z570 laptop with 750GB HDD, 6GB RAM, Intel i5 Processor and Windows 7 installed in it. I also have an external portable USB hard-disk of 1TB.
My aim was to install Ubuntu 12.10 onto the external hard disk including Grub boot loader onto it too.
I use my external hard disk to store my backup data. In order to install Linux onto it I made some free space in the hard about 50 GB using Windows partition tool. I successfully did it without loosing any data.
Then I downloaded Ubuntu 12.10 32bit ISO, made an boot-able USB, and I booted into Ubuntu successfully. I then went on with installing Ubuntu. I carefully selected my 1TB external hard disk found out the free space I had created earlier, and made 4 partition on it
1. \boot ext4 1024 MB 2. \ ext4 5120 MB 3. swap 6144 MB 4. \home ext4 32768 MB
And I selected
\boot partition to install GRUB into it.
and everything went on smoothly.
When I restarted the computer after installing Ubuntu it directly loaded Windows 7. So I restarted it, changed the boot priority to USB HDD and when I booted into it, it showed the next error:
ntldr missing Press Ctrl+Alt+Del to restart