We are running Windows Server 2008 x64 version on an HP server with 64-logical CPUs. One of the applications that we currently use is 32-bit (and therefore running under WOW64) fails when running in this environment. If we change the hardware configuration so that there are only 32 logical CPUs then everything works ok. The problem can be reproduced using the test code provided in this post http://groups.google.com/group/microsoft.public.dotnet.framework/browse_thread/thread/15f1651aae32c97a/2815780668f96866?q=system.threading.timer+sp1+server+2003&rnum=1&hl=en (this was for a completely different problem, but illustrates the problem). I know that there is a limit of 32-CPUs on the 32-bit version of Windows Server 2008, so is that what is causing the application to fail ? If so, is it possible to configure WOW64 to only use 32 of the 64 available CPUs ?

Hi, Please have a look at the following articles: Best Practices for WOW64 http://www.microsoft.com/whdc/system/platform/64bit/WoW64_bestprac.mspx Running 32-bit Applications http://msdn.microsoft.com/en-us/library/aa384249(VS.85).aspx If the problem continues, you may also ask in the MSDN forum: http://social.msdn.microsoft.com/Forums/en-US/categories Regards, Bruce

We re-installed with Windows Server 2008 R2 x64 on the same hardware platform. After doing this the problem was no longer reproduceable. Therefore this looks to be a bug / limitation / feature in Windows Server 2008.