diff --git a/reactos/lib/kernel32/misc/comm.c b/reactos/lib/kernel32/misc/comm.c
index a1fdeab597c..0615e1abdb3 100644
--- a/reactos/lib/kernel32/misc/comm.c
+++ b/reactos/lib/kernel32/misc/comm.c
@@ -834,7 +834,7 @@ STDCALL
 CommConfigDialogA(LPCSTR lpszName, HWND hWnd, LPCOMMCONFIG lpCC)
 {
 	PWCHAR NameW;
-	BOOL result;
+	DWORD result;
 
 	/* don't use the static thread buffer so operations in serialui
 	   don't overwrite the string */
@@ -858,9 +858,9 @@ BOOL
 STDCALL
 CommConfigDialogW(LPCWSTR lpszName, HWND hWnd, LPCOMMCONFIG lpCC)
 {
-	BOOL (STDCALL *drvCommDlgW)(LPCWSTR, HWND, LPCOMMCONFIG);
+	DWORD (STDCALL *drvCommDlgW)(LPCWSTR, HWND, LPCOMMCONFIG);
 	HMODULE hSerialuiDll;
-	BOOL result;
+	DWORD result;
 
 	//FIXME: Get dll name from registry. (setupapi needed)
 	if(!(hSerialuiDll = LoadLibraryW(L"serialui.dll")))
@@ -869,7 +869,8 @@ CommConfigDialogW(LPCWSTR lpszName, HWND hWnd, LPCOMMCONFIG lpCC)
 		return FALSE;
 	}
 
-	drvCommDlgW = GetProcAddress(hSerialuiDll, "drvCommConfigDialogW");
+	drvCommDlgW = (DWORD (STDCALL *)(LPCWSTR, HWND, LPCOMMCONFIG))
+					GetProcAddress(hSerialuiDll, "drvCommConfigDialogW");
 
 	if(!drvCommDlgW)
 	{
@@ -879,8 +880,10 @@ CommConfigDialogW(LPCWSTR lpszName, HWND hWnd, LPCOMMCONFIG lpCC)
 	}
 
 	result = drvCommDlgW(lpszName, hWnd, lpCC);
+	SetLastError(result);
 	FreeLibrary(hSerialuiDll);
-	return result;
+	
+	return (result == ERROR_SUCCESS ? TRUE : FALSE);
 }
 
 
diff --git a/reactos/lib/serialui/serialui.c b/reactos/lib/serialui/serialui.c
index ba9461bef70..0cbfaf489cd 100644
--- a/reactos/lib/serialui/serialui.c
+++ b/reactos/lib/serialui/serialui.c
@@ -98,7 +98,7 @@ DllMain(HINSTANCE hInstance,
 /*
  * @implemented
  */
-BOOL WINAPI drvCommConfigDialogW(LPCWSTR lpszDevice,
+DWORD WINAPI drvCommConfigDialogW(LPCWSTR lpszDevice,
 	HWND hWnd,
 	LPCOMMCONFIG lpCommConfig)
 {
@@ -106,7 +106,7 @@ BOOL WINAPI drvCommConfigDialogW(LPCWSTR lpszDevice,
 
 	if(!lpszDevice || !lpCommConfig)
 	{
-		return FALSE;
+		return ERROR_INVALID_PARAMETER;
 	}
 
 	DialogInfo.lpszDevice = lpszDevice;
@@ -119,7 +119,7 @@ BOOL WINAPI drvCommConfigDialogW(LPCWSTR lpszDevice,
 /*
  * @implemented
  */
-BOOL WINAPI drvCommConfigDialogA(LPCSTR lpszDevice,
+DWORD WINAPI drvCommConfigDialogA(LPCSTR lpszDevice,
 	HWND hWnd,
 	LPCOMMCONFIG lpCommConfig)
 {
@@ -136,13 +136,13 @@ BOOL WINAPI drvCommConfigDialogA(LPCSTR lpszDevice,
 		return result;
 	}
 	else
-		return FALSE;
+		return ERROR_NOT_ENOUGH_MEMORY;
 }
 
 /*
  * @unimplemented
  */
-BOOL WINAPI drvSetDefaultCommConfigW(LPCWSTR lpszDevice,
+DWORD WINAPI drvSetDefaultCommConfigW(LPCWSTR lpszDevice,
 	LPCOMMCONFIG lpCommConfig,
 	DWORD dwSize)
 {
@@ -152,7 +152,7 @@ BOOL WINAPI drvSetDefaultCommConfigW(LPCWSTR lpszDevice,
 /*
  * @unimplemented
  */
-BOOL WINAPI drvSetDefaultCommConfigA(LPCSTR lpszDevice,
+DWORD WINAPI drvSetDefaultCommConfigA(LPCSTR lpszDevice,
 	LPCOMMCONFIG lpCommConfig,
 	DWORD dwSize)
 {
@@ -162,7 +162,7 @@ BOOL WINAPI drvSetDefaultCommConfigA(LPCSTR lpszDevice,
 /*
  * @unimplemented
  */
-BOOL WINAPI drvGetDefaultCommConfigW(LPCWSTR lpszDevice,
+DWORD WINAPI drvGetDefaultCommConfigW(LPCWSTR lpszDevice,
 	LPCOMMCONFIG lpCommConfig,
 	LPDWORD lpdwSize)
 {
@@ -172,7 +172,7 @@ BOOL WINAPI drvGetDefaultCommConfigW(LPCWSTR lpszDevice,
 /*
  * @unimplemented
  */
-BOOL WINAPI drvGetDefaultCommConfigA(LPCSTR lpszDevice,
+DWORD WINAPI drvGetDefaultCommConfigA(LPCSTR lpszDevice,
 	LPCOMMCONFIG lpCommConfig,
 	LPDWORD lpdwSize)
 {
@@ -231,7 +231,7 @@ LRESULT CommDlgProc(HWND hDlg,
 
 			/* Initialize baud rate combo */
 			if(!(hBox = GetDlgItem(hDlg, IDC_BAUDRATE)))
-				EndDialog(hDlg, 0);
+				EndDialog(hDlg, ERROR_CANCELLED);
 
 			for(i = 0; Bauds[i]; i++)
 			{
@@ -246,7 +246,7 @@ LRESULT CommDlgProc(HWND hDlg,
 
 			/* Initialize byte size combo */
 			if(!(hBox = GetDlgItem(hDlg, IDC_BYTESIZE)))
-				EndDialog(hDlg, 0);
+				EndDialog(hDlg, ERROR_CANCELLED);
 
 			for(i = 0; ByteSizes[i]; i++)
 			{
@@ -261,7 +261,7 @@ LRESULT CommDlgProc(HWND hDlg,
 
 			/* Initialize parity combo */
 			if(!(hBox = GetDlgItem(hDlg, IDC_PARITY)))
-				EndDialog(hDlg, 0);
+				EndDialog(hDlg, ERROR_CANCELLED);
 
 			for(i = 0; Parities[i].StrId; i++)
 			{
@@ -278,7 +278,7 @@ LRESULT CommDlgProc(HWND hDlg,
 
 			/* Initialize stop bits combo */
 			if(!(hBox = GetDlgItem(hDlg, IDC_STOPBITS)))
-				EndDialog(hDlg, 0);
+				EndDialog(hDlg, ERROR_CANCELLED);
 
 			for(i = 0; StopBits[i].StrId; i++)
 			{
@@ -295,7 +295,7 @@ LRESULT CommDlgProc(HWND hDlg,
 
 			/* Initialize flow control combo */
 			if(!(hBox = GetDlgItem(hDlg, IDC_FLOW)))
-				EndDialog(hDlg, 0);
+				EndDialog(hDlg, ERROR_CANCELLED);
 
 			if(LoadStringW(hDllInstance, IDS_FC_NO, wstr, sizeof(wstr) / sizeof(wstr[0])))
 			{
@@ -337,11 +337,11 @@ LRESULT CommDlgProc(HWND hDlg,
 			switch(wParam)
 			{
 				case IDC_CANCELBTN:
-					EndDialog(hDlg, FALSE);
+					EndDialog(hDlg, ERROR_CANCELLED);
 					break;
 				case IDC_OKBTN:
 					OkButton(hDlg);
-					EndDialog(hDlg, TRUE);
+					EndDialog(hDlg, ERROR_SUCCESS);
 					break;
 			}
 			return TRUE;
@@ -349,11 +349,11 @@ LRESULT CommDlgProc(HWND hDlg,
 
 		case WM_CLOSE:
 		{
-			EndDialog(hDlg, FALSE);
+			EndDialog(hDlg, ERROR_CANCELLED);
 			return TRUE;
 		} /* WM_CLOSE */
 
-			default:
+		default:
 			return FALSE;
 	}
 
diff --git a/reactos/lib/serialui/serialui.h b/reactos/lib/serialui/serialui.h
index e998a2117d7..ba293ca185d 100644
--- a/reactos/lib/serialui/serialui.h
+++ b/reactos/lib/serialui/serialui.h
@@ -11,8 +11,7 @@
 #include "resource.h"
 
 #define UNIMPLEMENTED \
-  SetLastError(ERROR_CALL_NOT_IMPLEMENTED); \
-  return FALSE;
+  return ERROR_CALL_NOT_IMPLEMENTED ;
 
 #define DEFAULT_BAUD_INDEX 6
 #define DEFAULT_BYTESIZE_INDEX 3
@@ -45,27 +44,27 @@ typedef struct _STOPBIT_INFO
  *
  ************************************/
 
-BOOL WINAPI drvCommConfigDialogW(LPCWSTR lpszDevice,
+DWORD WINAPI drvCommConfigDialogW(LPCWSTR lpszDevice,
 	HWND hWnd,
 	LPCOMMCONFIG lpCommConfig);
 
-BOOL WINAPI drvCommConfigDialogA(LPCSTR lpszDevice,
+DWORD WINAPI drvCommConfigDialogA(LPCSTR lpszDevice,
 	HWND hWnd,
 	LPCOMMCONFIG lpCommConfig);
 
-BOOL WINAPI drvSetDefaultCommConfigW(LPCWSTR lpszDevice,
+DWORD WINAPI drvSetDefaultCommConfigW(LPCWSTR lpszDevice,
 	LPCOMMCONFIG lpCommConfig,
 	DWORD dwSize);
 
-BOOL WINAPI drvSetDefaultCommConfigA(LPCSTR lpszDevice,
+DWORD WINAPI drvSetDefaultCommConfigA(LPCSTR lpszDevice,
 	LPCOMMCONFIG lpCommConfig,
 	DWORD dwSize);
 
-BOOL WINAPI drvGetDefaultCommConfigW(LPCWSTR lpszDevice,
+DWORD WINAPI drvGetDefaultCommConfigW(LPCWSTR lpszDevice,
 	LPCOMMCONFIG lpCommConfig,
 	LPDWORD lpdwSize);
 
-BOOL WINAPI drvGetDefaultCommConfigA(LPCSTR lpszDevice,
+DWORD WINAPI drvGetDefaultCommConfigA(LPCSTR lpszDevice,
 	LPCOMMCONFIG lpCommConfig,
 	LPDWORD lpdwSize);