I recently had to install ESXi onto a server without a cdrom drive fitted, the quickest and easiest method for me to do this was installing ESXi using VMware Player or Workstation and installing it directly onto the USB key.
Choose the Typical Wizard
Browse to your ISO file.
Define the name and location where you’re going to store the files.
Un-tick the Power on VM box because we are going to edit the VM settings after we finish, it’s no good clicking customize hardware at this point because the HDD hasn’t been created yet.
Here we can see the VM hardware settings, we are going to delete the floppy and HDD to reduce overhead.
Next we need to power on the VM and then attach the USB device to it. Browse to the Home on Workstation or Player
Right click on your VM and choose Power and the Power On.
Now we need to attach the USB to the VM.
Time to go through the installation.
The installation completes in a couple of minutes and then you’re good to go :). Let the system reboot and during the POST power off the VM and remove the USB drive.
Now take the USB key and plug it in to your Host and boot away 🙂