Maybe you’ve dug out that old server that you’ve had lying around for a while now and want to install VMware ESX or ESXi 4.0 on to it but upon doing so you get the following error message and things come to a grinding halt when going to start the installation process:

“Booting: MBI=0x000100d8, entry=0×00100212”

So what does this all mean?  Unfortunately it means that the CPU of the server you are trying to install ESX/ESXi 4.0 on to isn’t 64 bit compatible.  Although VMware ESX/ESXi 3.5 supported 32 bit processors the ESX/ESXi 4.0 version of VMware’s hypervisor does not.

Check out VMware’s Compatibility Guide here to confirm whether your server is compatible or not – though as Bas (see comments below) correctly points out the VMware HCL shouldn’t be taken as gospel as some servers not on the HCL will run ESX/ESXi (though just won’t be officially supported).

In my example below if I tried to install VMware ESXi 4.0 on my lab HP Proliant DL360 G3 we can see from the results of the VMware HCL lookup that this server only supports up to VMware ESX 3.5 U4 which is also confirmed by the fact that the Intel Xeon processor (Cranford) in this server aren’t 64 bit compatible.