One Server with 1x5410 Xeon (Quad Core) ..
Installed Windows Server 2008 Web x64 just fine .. Shutdown - put in a 2nd CPU - boot up :
Bluescreen :

Yes, both CPUs are identical .. I am wondering .. As the CPU is a quadcore - it should have installed the multi processor kernel anyway .. so why the heck throws it a blue screen when inserting a second CPU

I will now try to install it with both CPUs - which will probably work .. but this is just weird weird weird ...