It is possible to re-install android without losing windows. As donmorsa greatly pointed out, you need Intel's Flash Tool Lite. I used 64bit win 10.|
1) Power on the HiBook while holding volume up and volume down. You should get the Chuwi logo and the words "DNX FASTBOOT MODE.."
2) Windows on my machine didn't use the right driver. I had to manually change the "Intel Android AD" device driver to "Android Composite ADB Interface"
3) Once the driver was changed, the intel flash tool recognized the HiBook
4) Browse to where you extracted the HiBook Android.rar file. 7zip works great for extraction
5) Choose "update" in the configuration drop box.
6) Start the flash. For me, it got do 25% and stopped. The HiBook rebooted to the normal android recovery
7) Windows again got the driver wrong. The HiBook shows up as a different device, so I had to again manually select the "Android Composite ADB Interface"
8) I power cycled the HiBook,entering DNX boot and restarted the flash. This time it worked.
My HiBook now boots both windows and android.
Some other tidbits:
1) Press ESC or DEL to enter the BIOS at the CHUWI splash screen
2) Press F7 to get a boot device selection menu
3) The left and right arrows, followed by enter can select windows or android instead of the volume rocker