[Windows Central Question]

I have a tablet with Windows 8.1 and insufficient drive space for the 20 Gbyte upgrade to Windows 10. This a Teclast X89, dual OS with a Windows partition of 16 GB. Is the technical preview available for tablets and have system requirements for tablet upgrades to Windows 10 Mobile yet to be communicated?

[Nicholas Ek]

Windows 10 Mobile cannot be installed on existing tablets. Existing tablets with Windows 8.1 are only eligible for full Windows 10, not Mobile, even if they are 7-8".
However, the Windows 10 upgrade does NOT require 20 GBs. Your tablet is x86-based (32 bits) and the upgrade images are circa 2 GB, so if you have about 5 GB free, you should be fine. If your tablet cannot do an in-place upgrade to Windows 10, you can still do a clean install.

[Wp1876]

The teclast x89 contains the Intel Atom Z3735F, a 64 bit instruction set processor. The OEM OS is the 32 bit Windows with Bing. The problem with the above suggestions is that the maufacuter's partitioning of the 32 G drive leaves only 1.5 G free on the Windows parition, and a clean install will eliminate the dual boot.

[Nicholas Ek]

What does the Partition scheme look like? You can probably repartition the Windows 10 part of the storage through the Windows 10 installation USB.

[Wp1876]

The manufacturer has created 19 partitions, 2 EFI's, 1 recovery, and of course the Windows and Android partitions. I can find no documentation on the purpose of the remaining partitions. I don't read Chinese so the company forums have been of no use.

[Nicholas Ek]

How big is the Windows partition? 19 partitions is sure a lot though...

A clean install will not erase the Android partition(s). However, Windows by default overwrites the bootloader. I was looking into forums and I couldn't find any information on how the bootloader is currently implemented.

[Wp1876]

The Windows partition is 13 GB. The Windows Technet library states that Win 8, 8.1 has five default GPT partitions, the ESP which contains the bootloader, a partition for Win RE utilities, a MSR partition, the Windows OS, and a recovery partition. There is opaque reference to other system partitions that are optional. I have no confidence that the Windows installation will only write to the primary partitions that contain its utilities. The Android partition also appears as a primary partition.