Problem reinstalling Xubuntu 16.04

[MR ZenWiz]

Update:

I was able to put in an old hard drive that has both Windows 7 and
(X?)Ubuntu 11.04 on it.  Both boot, but I couldn't remember any of the
passwords.

I recovered the Windows password and was able to boot it all the way
up, but I still have to recover the Ubuntu password and try it.

The real question is this: why does it boot from this ancient 80GB
hard drive in two different OSes, but not from either of a 320 or
120GB hard drive that have Xubuntu on them?  I know it's not the disks
- they're both in good shape, and the 320GB one passed badblocks -w
checking.

One thing i forgot to mention, though I'm not sure how this owuld
matter - I've been running the laptop on the power cord, no battery.

How else can I check out the disk controller of the hardware to see if
it's that?

Thanks.