diff --git a/src/base/system.c b/src/base/system.c
index cb89cbbc4..58d39035c 100644
--- a/src/base/system.c
+++ b/src/base/system.c
@@ -2371,16 +2371,12 @@ int os_compare_version(int major, int minor)
 	mem_zero(&ver, sizeof(OSVERSIONINFO));
 	ver.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
 	GetVersionEx(&ver);
-	if(ver.dwMajorVersion > major && ver.dwMinorVersion > minor)
+	if(ver.dwMajorVersion > major || (ver.dwMajorVersion == major && ver.dwMinorVersion > minor))
 		return 1;
 	else if(ver.dwMajorVersion == major && ver.dwMinorVersion == minor)
 		return 0;
-	else if(ver.dwMajorVersion < major && ver.dwMinorVersion < minor)
+	else
 		return -1;
-	else 
-		return -2;
-#else
-	#error not implemented
 #endif
 }
 
diff --git a/src/engine/client/autoupdate.cpp b/src/engine/client/autoupdate.cpp
index 3cea537ea..aa701639b 100644
--- a/src/engine/client/autoupdate.cpp
+++ b/src/engine/client/autoupdate.cpp
@@ -25,7 +25,7 @@ void CAutoUpdate::Init()
 	m_pClient = Kernel()->RequestInterface<IClient>();
 	m_pStorage = Kernel()->RequestInterface<IStorage>();
 	m_pFetcher = Kernel()->RequestInterface<IFetcher>();
-	m_IsWinXP = (os_compare_version(5, 0) == 1 && os_compare_version(6, 0) == -1);
+	m_IsWinXP = os_compare_version(5, 1) <= 0;
 }
 
 void CAutoUpdate::ProgressCallback(CFetchTask *pTask, void *pUser)