I recently setup Ubuntu 12.10 on an external hard drive.

Here’s my setup:

HP Dragon Laptop

- Internal drive(sda) : 200GB (Windows Vista)
- External drive 1(sdb): USB hard drive (Buffalo 1.5TB)
- External drive 2(sdc): USB hard drive (Buffalo 1.5TB)
- External drive 3(sdd): USB hard drive with Linux partitions at the beginning (/boot, /, swap) followed by NTFS data partition, and with sdd set as the boot loader device (Buffalo 2.0TB)

When I first went to boot up from the external hard drive, I got the following error:

Non-system disc or disc error
replace and strike any key when ready

However, after disconnecting my other external hard drives I got the computer to boot into Ubuntu. Considering I have next to no experience with a Linux distro I'm quite pleased I got it to work at all. But if possible I would like to be able to boot into Ubuntu without having to unplug my other hard drives first.

My guess at the moment is that something that was pre-installed on one of the other drives is messing with the boot sequence causing problems booting up. Any one have an idea of how to fix this problem?