Temporary derail ...
Having found out about the bug photos purely by accident, this creature (which someone else has identified as
Arilus cristatus is known as the Wheel Bug, courtesy of that strange thoracic protrusion which resembles a gear wheel. That bug is
begging for a Photoshop steampunk makeover.
Now, back to our scheduled thread.
As to the internal hard drive to external hard drive conversion, it would require a lot of work. I don't know about SATA hard drives, but I suspect that with regard to power input, internal drives intended to live inside a desktop PC case have the same power connector as the older PATA drives (the ones that used to be called IDE or EIDE in the days before SATA existed). The power connectors for hard drives and CD-ROM/DVD-ROM drives have 4 wires attached to them, and each wire carries a different voltage. Which means you'd have to replicate that power supply to the drive, and the only way I know of doing that is to buy yourself a full-blown PC power supply unit and plug it into that. Then, you have all the fun of finding a way of interfacing the data connector to the outside world in such a way as to enable you to plug it into a USB port. Now, if SATA ports are compatible with USB ports signal wise, then this might not be a problem, but if they're not, you're looking at designing some fairly intricate electronics to provide the interfacing. Possibly involving putting together your own circuit board (and designing the thing from scratch using appropriate software), interfacing a brace of interesting ICs together to provide the signal conversion, and then testing the damn thing to make sure it doesn't blow up on you, preferably using a drive that you don't intend to
use long term. Then, you've got to parcel the whole thing into a box, and provide it with an external power cable to run the PSU. If the drive is a fast spinning one, you might consider sticking a big fan on top of it to keep it cool, and building some nice ventilation slots into the box the whole setup will live in.
Frankly, it's so much work that I'd wait until you find yourself needing a second PC to put it in, and save it for that.