diff --git a/StartupManager.cpp b/StartupManager.cpp
index e5afeeb..f8457f5 100644
--- a/StartupManager.cpp
+++ b/StartupManager.cpp
@@ -11,6 +11,39 @@ using namespace winrt::Windows::ApplicationModel;
 
 namespace {
     const wchar_t* kTaskId = L"TaskbarCalculatorStartup";
+    const wchar_t* kRunKey = L"Software\\Microsoft\\Windows\\CurrentVersion\\Run";
+    const wchar_t* kRunVal = L"TaskbarCalculator";
+
+    // --- HKCU\...\Run fallback (used when the app has no package identity) ---
+    bool RunKeyExists() {
+        HKEY h;
+        if (RegOpenKeyExW(HKEY_CURRENT_USER, kRunKey, 0, KEY_QUERY_VALUE, &h) != ERROR_SUCCESS)
+            return false;
+        LONG r = RegQueryValueExW(h, kRunVal, nullptr, nullptr, nullptr, nullptr);
+        RegCloseKey(h);
+        return r == ERROR_SUCCESS;
+    }
+
+    bool RunKeySet(bool on) {
+        HKEY h;
+        if (RegCreateKeyExW(HKEY_CURRENT_USER, kRunKey, 0, nullptr, 0,
+                            KEY_SET_VALUE, nullptr, &h, nullptr) != ERROR_SUCCESS)
+            return false;
+        LONG r;
+        if (on) {
+            wchar_t path[MAX_PATH];
+            GetModuleFileNameW(nullptr, path, MAX_PATH);
+            wchar_t quoted[MAX_PATH + 2];
+            wsprintfW(quoted, L"\"%s\"", path);
+            r = RegSetValueExW(h, kRunVal, 0, REG_SZ, (const BYTE*)quoted,
+                               (DWORD)((lstrlenW(quoted) + 1) * sizeof(wchar_t)));
+        } else {
+            r = RegDeleteValueW(h, kRunVal);
+            if (r == ERROR_FILE_NOT_FOUND) r = ERROR_SUCCESS;
+        }
+        RegCloseKey(h);
+        return r == ERROR_SUCCESS;
+    }
 }
 
 namespace Startup {
@@ -26,7 +59,8 @@ State Get() {
                 return State::Disabled;
         }
     } catch (...) {
-        return State::Unavailable;   // unpackaged / API missing
+        // Unpackaged (classic install): use the HKCU\Run fallback.
+        return RunKeyExists() ? State::Enabled : State::Disabled;
     }
 }
 
@@ -42,7 +76,7 @@ bool Set(bool on) {
             return true;
         }
     } catch (...) {
-        return false;
+        return RunKeySet(on);
     }
 }