Index: /trunk/src/VBox/Main/idl/VirtualBox.xidl
===================================================================
--- /trunk/src/VBox/Main/idl/VirtualBox.xidl	(revision 50379)
+++ /trunk/src/VBox/Main/idl/VirtualBox.xidl	(revision 50380)
@@ -2382,5 +2382,5 @@
 
       </desc>
-      <param name="id" type="uuid" mod="string" dir="in">
+      <param name="id" type="wstring" dir="in">
         <desc>Guest OS type ID string.</desc>
       </param>
Index: /trunk/src/VBox/Main/include/VirtualBoxImpl.h
===================================================================
--- /trunk/src/VBox/Main/include/VirtualBoxImpl.h	(revision 50379)
+++ /trunk/src/VBox/Main/include/VirtualBoxImpl.h	(revision 50380)
@@ -297,5 +297,5 @@
                        BOOL aForceNewUuid,
                        ComPtr<IMedium> &aMedium);
-    HRESULT getGuestOSType(const com::Guid &aId,
+    HRESULT getGuestOSType(const com::Utf8Str &aId,
                            ComPtr<IGuestOSType> &aType);
     HRESULT createSharedFolder(const com::Utf8Str &aName,
Index: /trunk/src/VBox/Main/src-server/VirtualBoxImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/src-server/VirtualBoxImpl.cpp	(revision 50379)
+++ /trunk/src/VBox/Main/src-server/VirtualBoxImpl.cpp	(revision 50380)
@@ -1842,10 +1842,9 @@
 
 /** @note Locks this object for reading. */
-HRESULT VirtualBox::getGuestOSType(const com::Guid &aId,
+HRESULT VirtualBox::getGuestOSType(const com::Utf8Str &aId,
                                    ComPtr<IGuestOSType> &aType)
 {
     aType = NULL;
     AutoReadLock alock(m->allGuestOSTypes.getLockHandle() COMMA_LOCKVAL_SRC_POS);
-    IN_BSTR strId = Bstr(aId.toUtf16()).raw();
 
     HRESULT rc = S_OK;
@@ -1856,5 +1855,5 @@
         const Bstr &typeId = (*it)->i_id();
         AssertMsg(!typeId.isEmpty(), ("ID must not be NULL"));
-        if (com::Guid(typeId) == aId)
+        if (typeId == aId)
         {
             (*it).queryInterfaceTo(aType.asOutParam());
@@ -1864,6 +1863,6 @@
     return (aType) ? S_OK :
         setError(E_INVALIDARG,
-                 tr("'%ls' is not a valid Guest OS type"),
-                 strId);
+                 tr("'%s' is not a valid Guest OS type"),
+                 aId.c_str());
     return rc;
 }