I'm Fairly new at this, Decided I'd try running Ubuntu server on an ext. hard drive. Not sure how to do it, decided I'd be careful, maybe ask some other people who know. Any help on this would be much appreciated.
I did something like this on a Western Digital hard drive. Seems like it should work. I thought the USB 2 connection was a bottleneck on speed for the OS, but good enough for testing.
You may need to change the boot order in the BIOS, or use something like PLoP Boot manager.
As the others above said, if it has a USB interface, I'm fairly certain you could just boot it from the BIOS menu. (Hold F2 when powering on your computer, should be fairly straightforward from there.)
Ah, I misspoke, I meant that I wish to INSTALL the Server distro on to an ext. hard drive while retaining my PC's OS. I'm fairly certain I should be able to do it with a flash drive and the ext. drive, but the problem arises in not understanding how to install to a drive that isn't primary in the BIOS.
Typically, installers let you specify the destination devices. Until you get beyond that point, nothing bad will happen to your system. If you are really concerned, however, you can install from a CD, and physically disconnect the internal drive.