diff --git a/src/install.sh b/src/install.sh
index 91ab221..e8b5e23 100644
--- a/src/install.sh
+++ b/src/install.sh
@@ -1,41 +1,70 @@
 #!/usr/bin/env bash
 set -Eeuo pipefail
 
+: "${EXTERNAL:="N"}"
 : "${ATTENDED:="N"}"
 : "${VERSION:="win11x64"}"
 
-# Display wait message
-MSG="Please wait while Windows is being downloaded..."
-/run/server.sh "Windows" "$MSG" &
-
 ARGUMENTS="-chardev socket,id=chrtpm,path=/dev/shm/emulated_tpm/swtpm-sock $ARGUMENTS"
 ARGUMENTS="-tpmdev emulator,id=tpm0,chardev=chrtpm -device tpm-tis,tpmdev=tpm0 $ARGUMENTS"
 
-BASE="$VERSION.iso"
+[[ "${VERSION,,}" == "http"* ]] && EXTERNAL="Y"
+MSG="Please wait while Windows is being started..."
+
+if [ ! -f "$STORAGE/custom.iso" ]; then
+  if [[ "$EXTERNAL" != [Yy1]* ]]; then
+
+    if [ ! -f "$STORAGE/$VERSION.iso" ]; then
+      MSG="Please wait while Windows is being downloaded..."
+    fi
+
+  else
+
+    BASE=$(basename "$VERSION")
+    if [ ! -f "$STORAGE/$BASE" ]; then
+      MSG="Please wait while '$BASE' is being downloaded..."
+    fi
+
+  fi
+fi
+
+# Display wait message
+/run/server.sh "Windows" "$MSG" &
+
+BASE="custom.iso"
 [ -f "$STORAGE/$BASE" ] && return 0
 
-#if [ -f "$STORAGE/data.qcow2" ]; then
-#  error "Cannot download ISO '$VERSION' while there is an existing hard disk file present (data.qcow2)."
-#  error "If you are sure that the disk contains nothing important, delete it manually and restart the container."
-#  exit 68
-#fi
+BASE="Custom.iso"
+[ -f "$STORAGE/$BASE" ] && return 0
+
+BASE="custom.ISO"
+[ -f "$STORAGE/$BASE" ] && return 0
+
+BASE="CUSTOM.iso"
+[ -f "$STORAGE/$BASE" ] && return 0
+
+BASE="CUSTOM.ISO"
+[ -f "$STORAGE/$BASE" ] && return 0
+
+if [[ "$EXTERNAL" != [Yy1]* ]]; then
+
+  BASE="$VERSION.iso"
+
+else
+
+  BASE=$(basename "$VERSION")
+
+fi
+
+[ -f "$STORAGE/$BASE" ] && return 0
 
 TMP="$STORAGE/tmp"
 rm -rf "$TMP" && mkdir -p "$TMP"
 
-if [ -f "$STORAGE/custom.iso" ]; then
+ISO="$TMP/$BASE"
+rm -f "$ISO"
 
-  ATTENDED="Y"
-  LABEL="Custom"
-  cp "$STORAGE/custom.iso" "$TMP/$BASE"
-
-else
-
-  LABEL="$VERSION"
-
-fi
-
-if [ ! -f "$TMP/$BASE" ]; then
+if [[ "$EXTERNAL" != [Yy1]* ]]; then
 
   SCRIPT="$TMP/mido.sh"
 
@@ -47,8 +76,29 @@ if [ ! -f "$TMP/$BASE" ]; then
   rm -f "$SCRIPT"
   cd /run
 
-  [ ! -f "$TMP/$BASE" ] && error "Failed to download '$VERSION' from the Microsoft servers!" && exit 66
+else
 
+  info "Downloading $BASE as boot image..."
+
+  # Check if running with interactive TTY or redirected to docker log
+  if [ -t 1 ]; then
+    PROGRESS="--progress=bar:noscroll"
+  else
+    PROGRESS="--progress=dot:giga"
+  fi
+
+  { wget "$VERSION" -O "$ISO" -q --no-check-certificate --show-progress "$PROGRESS"; rc=$?; } || :
+
+  (( rc != 0 )) && error "Failed to download $VERSION, reason: $rc" && exit 60
+
+fi
+
+[ ! -f "$ISO" ] && error "Failed to download $VERSION" && exit 61
+
+SIZE=$(stat -c%s "$ISO")
+
+if ((SIZE<10000000)); then
+  error "Invalid ISO file: Size is smaller than 10 MB" && exit 62
 fi
 
 info "Preparing ISO image for installation..."
@@ -56,25 +106,29 @@ info "Preparing ISO image for installation..."
 DIR="$TMP/unpack"
 rm -rf "$DIR"
 
-7z x "$TMP/$BASE" -o"$DIR"
+7z x "$ISO" -o"$DIR"
 
 if [[ "$ATTENDED" != [Yy1]* ]]; then
-  if [ -f "/run/assets/$VERSION.xml" ]; then
+  if [[ "$EXTERNAL" != [Yy1]* ]]; then
+    if [ -f "/run/assets/$VERSION.xml" ]; then
 
-    wimlib-imagex update "$DIR/sources/boot.wim" 2 \
-      --command "add /run/assets/$VERSION.xml /autounattend.xml"
+      wimlib-imagex update "$DIR/sources/boot.wim" 2 \
+        --command "add /run/assets/$VERSION.xml /autounattend.xml"
 
+    fi
   fi
 fi
 
-OUT="$TMP/$VERSION.tmp"
-rm -f "$OUT"
+LABEL="${BASE%.*}"
+ISO="$TMP/$LABEL.tmp"
+rm -f "$ISO"
 
 genisoimage -b boot/etfsboot.com -no-emul-boot -c BOOT.CAT -iso-level 4 -J -l -D -N -joliet-long -relaxed-filenames \
             -v -V "$LABEL" -udf -boot-info-table -eltorito-alt-boot -eltorito-boot efi/microsoft/boot/efisys_noprompt.bin \
-            -no-emul-boot -o "$OUT" -allow-limited-size "$DIR"
+            -no-emul-boot -o "$ISO" -allow-limited-size "$DIR"
+
+mv "$ISO" "$STORAGE/$BASE"
 
-mv "$OUT" "$STORAGE/$BASE"
 rm -rf "$TMP"
 
 return 0