I just put a 80GB hard drive in a USB 2.0 external enclosure & it only
indicates 31GB?????

I put another 20GB drive in a similar enclosure & it show 20GB

What's the deal

flyboysmb wrote:
You put the jumper on the wrong pins. You put the jumper in the
"clip" position. That limits the size of the disk, as declared to
the BIOS. Recheck your jumpers. That is where a 32GB limit
comes from.

Note that "clip" is not always documented on the label glued
to the drive. You may have to search the web site, for a more
complete list of jumper positions.

This is an example of a drive with complicated jumpering.
There is a small section that mentions clip (scroll down).

http://www.hitachigst.com/hdd/suppor.../d7k250jum.htm

Paul