I picked up some used HP T620 thin clients that had WES7 on them and I wanted to bump them to Win10 after it was released. The ones that I'm using have a 16GB mSATA SSD drives and 4GB of memory. I had to wait awhile for HP to get the 10 image out, but now you can install the HP Recovery Image Download Tool (ThinUpdate) 64-bit and that will help you build a USB stick with the Win10 IoT installer on it.
Be sure to get the free management software too: HP Device Manager
If your like me, you don't have the Win10 COA in the BIOS to activate this image, so it wants to block the install because the OS/BIOS check fails. Here is the work around:
Find this file on the flash drive: (Where your Flash drive is drive D:\)
Near the bottom, look for the deploy section and add -xb switch after IBRPE.EXE
REM - Deploy image. Remove C for OS
if exist C:\ call :REMOVEDRV C
%~dp0\IBRPE.EXE -xb %2 %1
Adding the -xb command line switch disables the OS/BIOS check
After the install completed, I was able to capture the image with HP Device manager and install it on my other thin clients. I did have to make separate images for both the Dual Core and Quad Core models.
Also, I have not been able to drop the IoT image over ThinOS. There must be something in the BIOS that blocks that. Let me know if you find a work-around.
Windows10 IoT is a specialized version of Enterprise, so you may be required to have a KMS server or Enterprise keys in order to activate. It activated off my KMS server just fine.