Alright guys, was wondering if someone could help me...

I've got an external hard drive, which only has media/documents on it, and have had it plugged in constantly to my computer for the past year or so. It seems to have become essential to my computer being able to start up correctly... if I unplug it, it says 'DISK BOOT FAILURE' and some little sign spins round while it tries to find it, then gives up.

Is my computer trying to use that drive to boot? I'm a bit confused as to why it would. Also, how can I change this, so that it isn't needed for my computer to start up?

thanks mate... a quick google search suggested something similar, but I'm not entirely sure what I'm doing in there. I'll give it a go, and hope my flatmate can repair any damage i do