what would happen if I took an xbox one s hard drive and put it in an xbox one x?

The internal hard drive is not meant to be swapped.

Pretty sure it was the update. I have two 5tb hard drives and my xbox one x and both xbox one s don't recognize the hard drives now.

The hard drive is only 1 TB. When the Xbox One S was first released it had a 2 TB hard drive. 1TB is not enough for hardcore gamers which is what this console seems to be intended for. The One X needs a 2 or 3TB hard drive. I understand the Xbox is trying
to keep the price down but the targeted consumer, hardcore gamers, are willing to pay extra for what we need. This will force the targeted consumer to use an external hard drive which to my understanding, and I may be wrong, will have a negative effect on
load times on the One X. If Xbox releases a One X at a later date with the necessary memory this will cause those of us that bought the console at release to feel betrayed. Different versions of the One X need to be released at launch like they did with the
One S giving us the choice of a 1 or 2TB console.

Hi there,

Connecting the drive up to a PC is not a good test to see if the drive is still working as an Xbox formatted drive won't show on a PC. The drive would need to be reformatted for the PC if you wanted to use it after it's been formatted for an Xbox One.

If you have a second console (of the same generation if possible - i.e. if it was on an Xbox One X, try it on an Xbox One S or X) try connecting it there to see if you get the same behavior. If you don't have a second in your procession, see if a friend/family
member has one that you can connect your drive to in order to do the check.

External hard drives can go bad at random times. It doesn't happen very often, but it can happen. I've had it happen to a hard drive I connected to my Xbox. I connected the drive to 3 different consoles and none of them read the drive. That's when I realized
the drive died.

yep. Put it on a hard drive and attach to the new xbox one s.