diff --git a/bootstrap-vitasdk.sh b/bootstrap-vitasdk.sh
index 5f5a059..4b93d94 100755
--- a/bootstrap-vitasdk.sh
+++ b/bootstrap-vitasdk.sh
@@ -7,11 +7,6 @@ INSTALLDIR="${VITASDK:-/usr/local/vitasdk}"
 
 . $DIR/include/install-vitasdk.sh
 
-if [ -d "$INSTALLDIR" ]; then
-  echo "$INSTALLDIR already exists. Remove it first (e.g. 'sudo rm -rf $INSTALLDIR' or 'rm -rf $INSTALLDIR') and then restart this script"
-  exit 1
-fi
-
 echo "==> Installing vitasdk to $INSTALLDIR"
 install_vitasdk $INSTALLDIR
 
diff --git a/include/install-vitasdk.sh b/include/install-vitasdk.sh
index 6713099..7b41043 100755
--- a/include/install-vitasdk.sh
+++ b/include/install-vitasdk.sh
@@ -1,7 +1,34 @@
 #!/bin/sh
 
 get_download_link () {
-  curl "https://api.github.com/repos/vitasdk/autobuilds/releases" | grep "master" | grep "browser_download_url" | grep $1 | head -n 1 | cut -d '"' -f 4
+  curl -sL "https://api.github.com/repos/vitasdk/autobuilds/releases" | grep "master" | grep "browser_download_url" | grep $1 | head -n 1 | cut -d '"' -f 4
+}
+
+need_root_perm () {
+  curr=$1
+  while true; do
+    if [ -d "$curr" ]; then
+      DIR_INFO=($(stat -Lc "%a %U %G" $curr))
+      PERM="0${DIR_INFO[0]}"
+      OWNER=${DIR_INFO[1]}
+      GROUP=${DIR_INFO[2]}
+      if [[ $(($PERM & 0200)) != 0 && $USER == $OWNER ]]; then
+        return
+      elif [ $(($PERM & 0002)) != 0 ]; then
+        return
+      elif [[ $(($PERM & 0020)) != 0 ]]; then
+        groups=($(groups $USER))
+        for grp in "${groups[@]}"; do
+          if [[ $GROUP == $grp ]]; then
+            return
+          fi
+        done
+      fi
+      echo 1
+      return
+    fi
+    curr=$(dirname $curr)
+  done
 }
 
 install_vitasdk () {
@@ -9,8 +36,11 @@ install_vitasdk () {
 
   case "$(uname -s)" in
      Darwin*)
+      if [ -d "$INSTALLDIR" ]; then
+          rm -rf $INSTALLDIR
+      fi
       mkdir -p $INSTALLDIR
-      wget -O "vitasdk-nightly.tar.bz2" "$(get_download_link osx)"
+      curl -o "vitasdk-nightly.tar.bz2" -L "$(get_download_link osx)"
       tar xf "vitasdk-nightly.tar.bz2" -C $INSTALLDIR --strip-components=1
       rm -f "vitasdk-nightly.tar.bz2"
      ;;
@@ -19,19 +49,30 @@ install_vitasdk () {
       if [ -n "${TRAVIS}" ]; then
           sudo apt-get install libc6-i386 lib32stdc++6 lib32gcc1 patch
       fi
-      if [ ! -d "$INSTALLDIR" ]; then
-        sudo mkdir -p $INSTALLDIR
-        sudo chown $USER:$(id -gn $USER) $INSTALLDIR
+      SUDO=
+      if [ ! -z "$(need_root_perm $INSTALLDIR)" ]; then
+        SUDO=sudo
+      fi
+      if [ -d "$INSTALLDIR" ]; then
+        $SUDO rm -rf $INSTALLDIR
+        if [ ! -z "$(need_root_perm $INSTALLDIR)" ]; then
+          SUDO=sudo
+        fi
       fi
-      wget -O "vitasdk-nightly.tar.bz2" "$(get_download_link linux)"
+      $SUDO mkdir -p $INSTALLDIR
+      $SUDO chown $USER:$(id -gn $USER) $INSTALLDIR
+      curl -o "vitasdk-nightly.tar.bz2" -L "$(get_download_link linux)"
       tar xf "vitasdk-nightly.tar.bz2" -C $INSTALLDIR --strip-components=1
       rm -f "vitasdk-nightly.tar.bz2"
      ;;
 
      MSYS*|MINGW64*)
       UNIX=false
+      if [ -d "$INSTALLDIR" ]; then
+          rm -rf $INSTALLDIR
+      fi
       mkdir -p $INSTALLDIR
-      wget -O "vitasdk-nightly.tar.bz2" "$(get_download_link mingw32)"
+      curl -o "vitasdk-nightly.tar.bz2" -L "$(get_download_link mingw32)"
       tar xf "vitasdk-nightly.tar.bz2" -C $INSTALLDIR --strip-components=1
       rm -f "vitasdk-nightly.tar.bz2"
      ;;