With the emulation mode set to "winxp" I can only TlsAlloc 64 indexes, even though the MSDN docs say there should be at least 20 million. http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dllproc/base/thread_local_storage.asp Has anyone done any work on this? Any workaround/hackarounds? ... mo