How To Change Program Files Location In Windows 10

I would ***NOT*** use a symbolic link/NTFS junction for this. Things may appear to work at first, but then something will break, a Windows Update will fail to install for no apparent reason, etc. I've tried this on 7, 8.1, and 10, this is always what happened. In short, there is no official way to move Program Files/Program Files (x86). Your best bet is to just manually choose the location you want when installing something.

I tried this method awhile back, it works fine, but requires a lot of manual work. I haven't tried it with 10 though. This method is very comprehensive and involves Registry editing/NTFS junctions. But I would first test it out thoroughly in a virtual machine before trying it on your real system. It's for Windows 7 but I had it working with 8.1 too:

http://bbearren.com/set7free/set7free.html

@messyjesse: If I were you, I would figure out which of your SSDs is faster, then install Windows onto that. Your OS should always be on the faster drive, your programs will run fine. You can use CrystalDiskMark for this. Just make sure to run the benchmark while nothing else significant is running. I would also recommend a minumum of 100GB so you have room for Windows, updates, drivers, you know, the critical stuff. Nothing worse than having to reinstall the OS later because you're low on space. It doesn't really matter whether it's bigger or smaller, as long as it's faster. You can always install certain programs onto either SSD, depending on where you want them to go. No advice other than that.

Do not do this- do not mess around with ProgramFilesDir.
Not unless you enjoy creating problems for yourself.

If you do, Windows upgrades (new major builds) will fail with a message you won't understand. (Likewise in-place upgrade repair installs of course).

Microsoft warns this is not supported. Please heed that.
To save space on C: manually install programs elsewhere if you absolutely have to (e.g. large games).
Better - move your personal data off C: which is very good practice. Think- if you have to reinstall your OS, your data would then be untouched.

I'd put it in my old laptop :)

That's actually what I did with a 128GB Kingston when I replaced it with a 250Gb Samsung EVO. My laptop is much happier.

IF you do that, you will NOT be able to upgrade your Windows to the next major build or do an in-place upgrade repair install. You will get a puzzling message if you try to do so.