Installing vmware EXSI 5.5 free i came across a problem on my HP XW6600, after the installation finished and the system rebooted. the only message i saw was “Non-System Disk or disk error …”, this error is because of lack of UEFI support on the XW6600, therefore the EXSI 5.x installer needs to be told to use MBR boot instead of UEFI boot..

When booting the installer you get the opportunity to press SHIFT+O to edit the boot options.

Then write at the prompt: formatwithmbr (remember to make a space between the runweasel and formatwithmbr)

Then follow the normal EXSI install and the XW6600 should boot withoput any problems.