Win10XPE Flat Boot - Black screen after startup

I am trying flat boot (extracted boot.wim structure on USB stick) with Win10XPE, and am using the boot.wim (64 bit) which works perfectly on all my test machines in RAMDISK mode. However, every machine shows the same behaviour... It boots up fine, gets to the point where it usually switches to admin user, flashes a few times, and then the screen turns black. It doesn't crash, and when I move the mouse/touchpad I can see the cursor moving, but it doesn't move on to the desktop. I dont have access to explorer or task manager to check anything in that state.

Just wondering if anybody tried this before and would have some hints on where the problem is. Sorry if I missed anything in the manual or tutorials.

Thanks!

One idea .... and if a well understand the issue...

Because it's a Flat winpe, you can easely modify the "system" hive and verify if a simple "CMD.exe" displays the good screen.
I assume Win10XPE use  the key : HKEY_LOCAL_MACHINE\SYSTEM\Setup\CmdLine = "a program"
You can test and change "a program" by "cmd.exe"
If "cmd" screen is ok, you can go step by step with the job of "a program".
I hope you can understand me ( my english is very poor ...)

PS : with my winpeBulder's PS scripts, i use winpe in ramdisk and also in flat mode : i don't see "your issue". Perhaps one program launched by "cmdline" searchs for some things in "Y:" or in the "boot" drive which may be different ( you don"t say if you expand in an VHD or in a real disk )

Just wanted to give an update.

I obviously did something wrong when I manually (using bootice) added the Flat Boot option to the boot menu.

After running: BCDboot P:\Windows /s P: /f ALL (P as an example) and using the programmatically created new boot options, PE booted up to the desktop OK. Not sure what I did wrong before.

One question remains though. How do I handle the Y drive assignment using flat boot? In other words, is it possible to use the same USB device for flat and Ramdisk boot? Obviously the USB drive now with flat boot becomes X (as it is now the system drive, before X was the "boot.wim" RAM drive), so it cannot be Y (programs folder) at the same time. I added a second partition to the usb drive, and moved the cdusb.y file and the programs folder there, but it still does not get the Y drive at startup. The letterswap logfile really did not help too much, as there was no output about finding the trigger file oder assiging drive Y. Is there another script/tool responsible for assigning the Y letter to the correct volume?

One more note: If I add the cdusb.y file and programs folder to an internal hard drive volume, the y drive is correctly assigned.

Seems to me that if you are Flat booting - then "Run All Programs From Ram" would be the Best Option for your Build...
You can then just copy the contents of the "Target" Folder to the USB and run your BCDboot command (whereas the P in your command would be the current Drive letter assigned to the USB stick) to make USB bootable...

I am pretty sure that with the information just provided, many others will be testing - Flat Booting
You can also Flat Boot from a separate Partition or a VHD(x) File..

Thanks for the hint!

What I tried for now (and what seems to work ok), is to use the subst command, to assign Y: to X:.

I added a line to the PECMD.INI file in the _PreShell section, right after the letterswap line. This works great regarding the Programs Folder and all the links.

My next step would be to call a cmd instead, and evaluate whether it's a flat or a RAMDISK boot, and act accordingly. What I also saw btw is that each time you boot up flat, a new user administrator profile is being created under x:\users, as the folder now is persistent (Administrator.Win10XPE.000, Administrator.Win10XPE.001,...). So a kind of cleanup logic is needed to wipe the rest at startup may be.

I forgot to mention completely why I was looking at flat boot at all. It just uses much less RAM, and I am still looking after some machines with less than 4 GB. Hope this ends somewhen ;)

Thanks!

seems to me that "Pecmd.ini" and "PEcmdAdmin.ini" would only have to run on "First" Boot - thus preventing the system configuration from re-processing upon next boot

You can also create a 'Normal" USB - then create a second Partition for Flat Boot Files...
then Add second (Flat Boot) Partition to "Normal" BCD using BCDBoot - just note the currently assigned drive letters on USB Partitions..
To "Display" the USB Boot Menu - Edit "Create ISO" Variable > %DisplayMenu%=True
Now when Booting the USB you should be presented with a "Boot Menu" > "Win10XPE" (Normal) and Windows 10 (Flat)
I also believe the "Normal" Partition will be assigned Y when Booting Normal or Flat - so may only need to expand "Boot.wim" to second Partition and leave "Programs" where is...
I have tested Flat Boot and Multi-boot long before with Project - but not with Y\Programs