If you're like me and didn't get the "Reserve Windows 10" app on your 32GB T100 or you just don't want to use it for whatever reason, there is an alternative way to upgrade your tablet from Windows 8.1 to Windows 10 which works very well and is quite easy to do.
You will need the following:
Asus TF Book T100 and Keyboard Dock (obviously)
A secondary PC
An empty USB flash drive
STEP 1 - Downloading the creation tool:
On your secondary PC insert a blank USB flash drive and download the media creation tool from the following link:
Windows 10
You should download the version that corresponds to your SECONDARY PC.
STEP 2 - Making a bootable drive:
Once you have downloaded the file, run it and choose "Create installation media for another PC.
Click next and you will be asked for a language, edition and architecture.
For language, pick whatever applies to you. However for edition and architecture it is very important that you choose the following:
Edition:
Windows 10 Home
Architecture:
32-bit (x86)
Setting edition to anything else may cause activation issues.
On the next page ensure that "USB flash drive" is selected and click next.
You will see a list of removable storage devices attached to your PC. Pick your flash drive and click next. THIS WILL DELETE ANY FILES THAT ARE ON THE DRIVE!!
Windows 10 will now be transferred to the drive. This may take some time so don't remove the drive until the program says that it has completed.
STEP 3 - Installing Windows 10:
Turn on your tablet and insert the drive into the USB port of the keyboard dock. Navigate to it and run the file named "setup.exe". Follow the onscreen instructions and once you do so Windows 10 will begin to install. This will take a while. For me it took almost 2 hours.
STEP 4 - Post installation tips:
This may not be the case for everyone, but in my experience, for the first 5 - 10 minutes, Windows 10 lagged very heavily but after this ran smooth as silk. I'd recommend just leaving the tablet alone for a while after installation.
If you're having problems getting the touch keyboard to work, installing the Windows updates seems to fix it.
Also a couple of the Asus apps are not compatible (eg Reading mode) and should be uninstalled for the time being if they are causing any problems.
Once you are certain that you want to stick with Windows 10, you can delete the folder "C:\Windows.old" to free up a couple of extra GBs of storage (Although keep in mind that you wont be able to easily revert back to 8.1 after doing this).
And there you have it! Windows 10 on your 32GB Asus T100. If you have any concerns or run into any problems, feel free to tell me below and I'll try to get back to you asap. Good luck!