diff --git a/worthless/installer.py b/worthless/installer.py
index a417f7e..105bd18 100644
--- a/worthless/installer.py
+++ b/worthless/installer.py
@@ -46,6 +46,17 @@ async def _download_file(file_url: str, file_name: str, file_path: Path | str, f
                 await f.write(chunk)
 
 
+def calculate_md5(file_to_calculate):
+    file_to_calculate = Path(file_to_calculate)
+    if not file_to_calculate.exists():
+        return ""
+    with file_to_calculate.open("rb") as f:
+        file_hash = hashlib.md5()
+        while chunk := f.read(8192):
+            file_hash.update(chunk)
+        return file_hash.hexdigest()
+
+
 class HDiffPatch:
     def __init__(self, git_url=None, data_dir=None):
         if not git_url:
@@ -397,6 +408,8 @@ class Installer:
         game = await self._get_game(pre_download)
         archive_name = game.latest.path.split("/")[-1]
         await self._download_file(game.latest.path, archive_name, game.latest.size)
+        if calculate_md5(self.temp_path.joinpath(archive_name)) != game.latest.md5:
+            raise RuntimeError("mismatch md5 for downloaded game archive")
 
     async def download_full_voiceover(self, language: str, pre_download=False):
         game = await self._get_game(pre_download)
@@ -413,16 +426,16 @@ class Installer:
             archive = Path(archive).resolve()
         if not archive.exists():
             raise FileNotFoundError(f"'{archive}' not found")
-        game_dir_str = str(self._gamedir)
-        if not game_dir_str.endswith("/"):
-            game_dir_str += "/"
-        print(f'-o"{game_dir_str}"')
-        proc = await asyncio.create_subprocess_shell(f'7z x {str(archive)} -o"{game_dir_str}"')
-        await proc.wait()
-        if proc.returncode != 0:
-            raise RuntimeError("Extracting failed")
-        # with zipfile.ZipFile(archive, 'r') as f:
-        #     await asyncio.to_thread(f.extractall, path=self._gamedir)
+        # game_dir_str = str(self._gamedir)
+        # if not game_dir_str.endswith("/"):
+        #     game_dir_str += "/"
+        # print(f'-o"{game_dir_str}"')
+        # proc = await asyncio.create_subprocess_shell(f'7z x {str(archive)} -o"{game_dir_str}"')
+        # await proc.wait()
+        # if proc.returncode != 0:
+        #     raise RuntimeError("Extracting failed")
+        with zipfile.ZipFile(archive, 'r') as f:
+            await asyncio.to_thread(f.extractall, path=self._gamedir)
 
     async def apply_voiceover(self, voiceover_archive: str | Path):
         # Since Voiceover packages are unclear about diff package or full package
@@ -517,18 +530,8 @@ class Installer:
     async def verify_from_pkg_version(self, pkg_version: AsyncPath, ignore_mismatch=False):
         contents = await pkg_version.read_text()
 
-        async def calculate_md5(file_to_calculate):
-            file_to_calculate = AsyncPath(file_to_calculate)
-            if not await file_to_calculate.exists():
-                return ""
-            async with file_to_calculate.open("rb") as f:
-                file_hash = hashlib.md5()
-                while chunk := await f.read(self._download_chunk):
-                    file_hash.update(chunk)
-                return file_hash.hexdigest()
-
         async def verify_file(file_to_verify, md5):
-            file_md5 = await calculate_md5(file_to_verify)
+            file_md5 = asyncio.to_thread(calculate_md5, file_to_verify)
             if file_md5 == md5:
                 return None
             if ignore_mismatch: