VMware: This system is not a supported platform

I encountered this error while installing HP branded Windows 2008 OEM on VMware ESXi 5.1.

This error occurs due to the check Windows performs to verify it is being installed on a HP branded machine.

Anyway this can be easily solved as stated in Installation of Microsoft Software Products Sold by HP (as OEM) on Virtual Machines Is Now Supported

Poweroff your VM, right click on it, choose Edit Settings -> Options and click Configuration Parameters

Now click Add Row and insert:

Name -> SMBIOS.reflectHost 

Value -> TRUE

as depicted in image below:

Click OK and poweron VM. This time you will be able to install Windows 2008 OEM correctly.

If you prefer you can manually edit the .vmx file of your virtual machine, using a text editor, adding a new line:

SMBIOS.reflectHost = TRUE

That's all!!