ASUS Ultrabook S500CA Motherboard Replacement Confusion


Jul 12, 2015
Hello, Tom's Comm,

It's been awhile. Thanks in advance for trying to help me out, especially as what is going on here is some confusion on what the manufacturer is putting in the thing.

Before I get into this, I will say that I do have desktop experience--I build my own boxes and OC--but am in unchartered water on replacing the motherboard on the following laptop. So, overall, my experience level is a little better than intermediate, I guess. On this, its noob/novice.

SYSTEM: ASUS Ultrabook S500CA-DS51T with 15.6" touchscreen and i5 processor. It has 2GB of RAM and runs Win 8.1. The case has an Ultrabook sticker. What the ASUS website seems to call it is a Vivobook. Here is a link:

This was my mother's work computer that she apparently killed a transistor on the MB that feeds the power from the box to the battery, by using a charger that wasn't the PC's actual charger (she was out of town and got into a bind because she did not have the PC charger with her). Because I do not own a laptop and am about to possibly return to school, and because I would like to learn what is on the inside of them and become as proficient upgrading one as I am desktops, I asked her to let me have it to work on, since it was dead and her company bought her a new one. I figured for maybe a $150 I could get a new board and upgrade the RAM and have a decent system. Maybe even add an SSD, for a tad more. And I can't hurt anything, as they bought her another.

That's where I am.


The laptop *case* designates this a S500CA-DS51T model computer. When I opened it up, the MB is stamped as an S400CA Rev. 2.1. I had thought to just buy the same board, but with an i7 processor onboard. Well, when you research it--there are several being sold on eBay--the S400CA board is listed as the 14" model board and comes in either a Rev. 2.1 or 3.1. However, what you see listed for the 15.6" laptop is a S500CA board (Revision number I cannot remember). So I am not sure what is going on there. I can get a board with an i7 on board in either version apparently, I just am not sure what will work.

So, that leads to these two questions:

1. Should I order a S500CA board or the S400CA that comes out of it?
2. If I need to go with the S400CA, does it matter which revision I get?
3. Seems like there was one more thing tied into this, but now I cannot remember it.

Anyway, I'm blond. So these people making this so confusing is really doing me dirty. True story.


My assumption is that even if I go with the exact same MB setup that is in the thing, I will have to reinstall Win 8.1, just as if I were upgrading a desktop. This, of course, would be doubly true if I replace the HDD with an SSD. The trick is, unlike MS always used to do desktops, there is no sticker on this thing with the activation code for Win 8.1. I hate Win 8.1 and only use Win 7 and 10 on anything else. I do have 7 Ultimate on CD (though I think it can only be installed on one PC at the time) and a bootable flash with Win 10 on it. What I had thought is that I would just wipe the thing and install Win 10 on it. The trick is, even if it still free do to so, won't I still need the product key for the Win 8.1 already on the laptop to authenticate 10? And, if so, where the devil would I come by it, by maybe by calling ASUS and giving them the serial number or something? I'm a bit stuck on that one. The only other thing I can think of is perhaps taking it to the Geek Squad and paying them to reinstall 8.1--I'm guessing they can get at the key somehow--but, man, I hate to do that.

Sorry to bug you all with the questions, but at 47-years-old, with me thinking of taking the last two semesters I need to have my degree, I will need a laptop. And this one seems like it would be okay, and that I could get out of it cheap. So I SURE would appreciate it if you guys could tell me how to go about this, as I really don't have discretionary income to put on a new one (or to waste on the wrong MB). Plus, I would really like to repair and upgrade this one so that I can learn from it, you know?

Anyway, thanks, G.


This should be the right motherboard. Go though the pictures and notes in the listing and compare to yours.

You should not need to re-install Windows, but you may need to contact MS to get it activated again.

The Ultrabook marking does not have anything to do with the laptop model, it's a branding thing for the slim laptops, like calling a tall station wagon an SUV. I think Intel came up with that name to show some specific features of a system, but in general, it's a higher end model that is slim.
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