diff --git a/Installer/DialogInstall.cpp b/Installer/DialogInstall.cpp
index f79bcc27..b86fb0c1 100644
--- a/Installer/DialogInstall.cpp
+++ b/Installer/DialogInstall.cpp
@@ -24,6 +24,10 @@
 #include "../Common/ControlTemplate.h"
 #include "../Common/Platform.h"
 
+#define APPNAME L"Rainmeter"
+
+const WCHAR* kRegistryInstallKey = L"SOFTWARE\\" APPNAME;
+
 CDialogInstall* CDialogInstall::c_Dialog = nullptr;
 
 HICON GetIcon(UINT id, bool large)
@@ -316,7 +320,7 @@ void CDialogInstall::TabContents::Create(HWND owner)
 			0, 43, 107, 9,
 			WS_VISIBLE, 0),
 
-		CT_EDIT(Id_DestinationEdit, 14,
+		CT_EDIT(Id_DestinationEdit, 0,
 			107, 40, 192, 14,
 			WS_VISIBLE | WS_TABSTOP | ES_AUTOHSCROLL | ES_READONLY, WS_EX_CLIENTEDGE),
 
@@ -335,16 +339,8 @@ void CDialogInstall::TabContents::Create(HWND owner)
 	ComboBox_AddString(item, L"English - English (United States)");
 	ComboBox_SetCurSel(item, 0);
 
-	item = GetControl(Id_InstallationTypeComboBox);
-	ComboBox_AddString(item, L"Standard 64-bit installation (reccomended)");
-	ComboBox_SetItemData(item, 0, MAKELPARAM(InstallType::Standard, InstallArch::X64));
-	ComboBox_AddString(item, L"Standard 32-bit installation");
-	ComboBox_SetItemData(item, 1, MAKELPARAM(InstallType::Standard, InstallArch::X32));
-	ComboBox_AddString(item, L"Portable 64-bit installation");
-	ComboBox_SetItemData(item, 2, MAKELPARAM(InstallType::Portable, InstallArch::X64));
-	ComboBox_AddString(item, L"Portable 32-bit installation");
-	ComboBox_SetItemData(item, 3, MAKELPARAM(InstallType::Portable, InstallArch::X32));
-	ComboBox_SetCurSel(item, 0);
+	PopulateInstallationTypes();
+	UpdateDestinationDirectory();
 }
 
 void CDialogInstall::TabContents::Initialize()
@@ -383,9 +379,117 @@ INT_PTR CDialogInstall::TabContents::OnCommand(WPARAM wParam, LPARAM lParam)
 		}
 		break;
 
+	case Id_InstallationTypeComboBox:
+	{
+		if (HIWORD(wParam) == CBN_SELCHANGE)
+		{
+			UpdateDestinationDirectory();
+		}
+		break;
+	}
+
 	default:
 		return FALSE;
 	}
 
 	return TRUE;
 }
+
+InstallType CDialogInstall::TabContents::GetInstallType()
+{
+	HWND item = GetControl(TabContents::Id_InstallationTypeComboBox);
+	const LPARAM typeData = ComboBox_GetItemData(item, ComboBox_GetCurSel(item));
+	return (InstallType)LOWORD(typeData);
+}
+
+InstallArch CDialogInstall::TabContents::GetInstallArch()
+{
+	HWND item = GetControl(TabContents::Id_InstallationTypeComboBox);
+	const LPARAM typeData = ComboBox_GetItemData(item, ComboBox_GetCurSel(item));
+	return (InstallArch)HIWORD(typeData);
+}
+
+void CDialogInstall::TabContents::PopulateInstallationTypes()
+{
+	HWND item = GetControl(Id_InstallationTypeComboBox);
+	int index = 0;
+	if (Util::IsSystem64Bit())
+	{
+		InstallArch existingArch;
+		const bool alreadyInstalled = IsAlreadyInstalled(existingArch);
+		if (!alreadyInstalled || existingArch == InstallArch::X64)
+		{
+			index = ComboBox_AddString(item, L"Standard 64-bit installation (recommended)");
+			ComboBox_SetItemData(item, index, MAKELPARAM(InstallType::Standard, InstallArch::X64));
+		}
+		if (!alreadyInstalled || existingArch == InstallArch::X32)
+		{
+			index = ComboBox_AddString(item, L"Standard 32-bit installation");
+			ComboBox_SetItemData(item, index, MAKELPARAM(InstallType::Standard, InstallArch::X32));
+		}
+		index = ComboBox_AddString(item, L"Portable 64-bit installation");
+		ComboBox_SetItemData(item, index, MAKELPARAM(InstallType::Portable, InstallArch::X64));
+	}
+	else
+	{
+		index = ComboBox_AddString(item, L"Standard 32-bit installation (recommended)");
+		ComboBox_SetItemData(item, index, MAKELPARAM(InstallType::Standard, InstallArch::X32));
+	}
+	index = ComboBox_AddString(item, L"Portable 32-bit installation");
+	ComboBox_SetItemData(item, index, MAKELPARAM(InstallType::Portable, InstallArch::X32));
+
+	ComboBox_SetCurSel(item, 0);
+}
+
+void CDialogInstall::TabContents::UpdateDestinationDirectory()
+{
+	WCHAR buffer[MAX_PATH];
+	buffer[0] = L'\0';
+
+	if (GetInstallType() == InstallType::Standard)
+	{
+		const bool hasRegistryKey = Util::GetRegistryString(
+			HKEY_LOCAL_MACHINE, kRegistryInstallKey, nullptr, buffer, _countof(buffer));
+		if (!hasRegistryKey)
+		{
+			const WCHAR* installPath =
+				GetInstallArch() == InstallArch::X32 ? L"%ProgramFiles%\\" APPNAME : L"%ProgramW6432%\\" APPNAME;
+			ExpandEnvironmentStrings(installPath, buffer, _countof(buffer));
+		}
+	}
+	else
+	{
+		ExpandEnvironmentStrings(L"%SystemDrive%\\" APPNAME, buffer, _countof(buffer));
+	}
+
+	HWND item = GetControl(Id_DestinationEdit);
+	Edit_SetText(item, buffer);
+}
+
+bool CDialogInstall::TabContents::IsAlreadyInstalled(InstallArch& arch)
+{
+	WCHAR buffer[MAX_PATH];
+	const bool hasRegistryKey = Util::GetRegistryString(
+		HKEY_LOCAL_MACHINE, kRegistryInstallKey, nullptr, buffer, _countof(buffer));
+	if (hasRegistryKey)
+	{
+		PathAppend(buffer, L"Rainmeter.exe");
+		if (PathFileExists(buffer))
+		{
+			// FIXME: This is an ugly way to check if Rainmeter.exe is 32-bit.
+			HMODULE rainmeterExe = LoadLibrary(buffer);
+			if (rainmeterExe)
+			{
+				arch = InstallArch::X32;
+				CloseHandle(rainmeterExe);
+			}
+			else
+			{
+				arch = InstallArch::X64;
+			}
+			return true;
+		}
+	}
+
+	return false;
+}
diff --git a/Installer/DialogInstall.h b/Installer/DialogInstall.h
index 88584030..a0ce13eb 100644
--- a/Installer/DialogInstall.h
+++ b/Installer/DialogInstall.h
@@ -19,6 +19,7 @@
 #ifndef RM_INSTALLER_DIALOGINSTALL_H_
 #define RM_INSTALLER_DIALOGINSTALL_H_
 
+#include "Install.h"
 #include "../Common/Dialog.h"
 
 class CDialogInstall : public Dialog
@@ -52,6 +53,14 @@ protected:
 		void Create(HWND owner);
 		virtual void Initialize();
 
+		InstallType GetInstallType();
+		InstallArch GetInstallArch();
+
+		void PopulateInstallationTypes();
+		void UpdateDestinationDirectory();
+
+		bool IsAlreadyInstalled(InstallArch& arch);
+
 	protected:
 		virtual INT_PTR HandleMessage(UINT uMsg, WPARAM wParam, LPARAM lParam);
 		INT_PTR OnCommand(WPARAM wParam, LPARAM lParam);
diff --git a/Installer/StdAfx.h b/Installer/StdAfx.h
index 0dbf5234..0b582c4d 100644
--- a/Installer/StdAfx.h
+++ b/Installer/StdAfx.h
@@ -19,7 +19,6 @@
 #ifndef RM_INSTALLER_STDAFX_H_
 #define RM_INSTALLER_STDAFX_H_
 
-#define WIN32_LEAN_AND_MEAN
 #include <windows.h>
 #include <windowsx.h>
 #include <commctrl.h>
diff --git a/Installer/Util.cpp b/Installer/Util.cpp
index d6beb441..b2728c3d 100644
--- a/Installer/Util.cpp
+++ b/Installer/Util.cpp
@@ -184,9 +184,10 @@ bool GetRegistryDword(HKEY rootKey, const WCHAR* subKey, const WCHAR* value, DWO
 		type == REG_DWORD);
 }
 
-bool GetRegistryString(HKEY rootKey, const WCHAR* subKey, const WCHAR* value, WCHAR* data, DWORD dataSize)
+bool GetRegistryString(HKEY rootKey, const WCHAR* subKey, const WCHAR* value, WCHAR* data, DWORD bufferLength)
 {
 	DWORD type;
+	DWORD dataSize = bufferLength * sizeof(data[0]);
 	return (SHGetValue(rootKey, subKey, value, &type, data, &dataSize) == ERROR_SUCCESS &&
 		type == REG_SZ);
 }