fix writing by using a virtual image instead of a physical thumbdrive, better document the hack in KeIrqDispatch

build.bat

@@ -3,7 +3,12 @@ setlocal enabledelayedexpansion
 
 set ROOT=%~dp0.
 set SRC=%ROOT%\code
-set DEST=%NTLITE_DRIVE%
+set VHD=%~dp0disk.vhd
+
+if not exist "%VHD%" (
+    echo ERROR: disk.vhd not found. Run mkimage.bat first.
+    exit /b 1
+)
 
 if exist "obj" rd /s /q "obj"
 if exist "bin" rd /s /q "bin"
@@ -129,6 +134,26 @@ echo Linking video.exe...
 link %LFLAGS% /SUBSYSTEM:NATIVE /ENTRY:main ^
     /OUT:"bin\video.exe" /PDB:"bin\video.pdb" bin\win32.lib obj\libc.obj %SRC%\video\bink2w64.lib obj\video\*.obj || exit /b 1
 
+:: ---- Mount disk image ----
+echo Mounting disk.vhd as Z: ...
+set DPS=%TEMP%\ntlite_mnt_%RANDOM%.txt
+(
+    echo select vdisk file="%VHD%"
+    echo attach vdisk
+    echo select partition 1
+    echo assign letter=Z
+    echo exit
+) > "%DPS%"
+diskpart /s "%DPS%"
+del "%DPS%"
+
+if not exist "Z:\" (
+    echo ERROR: Could not mount disk.vhd as Z:
+    echo If Z: is already in use, change the letter in build.bat and mkimage.bat.
+    exit /b 1
+)
+set DEST=Z:
+
 :: ---- Copy to ESP layout ----
 echo Assembling ESP...
 mkdir "%DEST%\drivers" 2>nul
@@ -147,6 +172,18 @@ copy /y "bin\shell.exe"   "%DEST%\"
 copy /y "bin\video.exe"   "%DEST%\"
 copy /y "%SRC%\boot.ini"  "%DEST%\"
 copy /y "%SRC%\drivers\drivers.ini" "%DEST%\drivers\"
+if exist "%SRC%\video\bink2w64.dll" copy /y "%SRC%\video\bink2w64.dll" "%DEST%\"
+
+:: ---- Unmount disk image ----
+echo Unmounting disk.vhd...
+set DPS=%TEMP%\ntlite_umnt_%RANDOM%.txt
+(
+    echo select vdisk file="%VHD%"
+    echo detach vdisk
+    echo exit
+) > "%DPS%"
+diskpart /s "%DPS%"
+del "%DPS%"
 
 echo.
 echo Build complete.