Here’s a quick tip on how to create a bootable USB flash drive from which you can install ESXi.

1. Download UNetbootin (available for Windows and Linux).
2. Download the latest ESXi .iso file from VMware.
3. Format your USB flash drive (1 to 2 GB should work, I used a 4 GB one) with a FAT32 file system.
4. Fire up UNetbootin and select the option to use your own .iso file.
5. Make sure you choose the RIGHT USB flash drive — Best Practice would be to have only your target drive connected while doing this!
6. Click OK and let it cook. This may take a few minutes.
7. Cancel the prompt at the end to reboot — you don’t want to reboot, really.
8. Unmount your USB flash drive and test it on ESXi compatible hardware!

There are some limitations to this method:

• Target system must support USB boot (very few don’t)
• Won’t work with an EFI BIOS unless that BIOS supports booting a legacy mode BIOS. Even then, it still may not work.

And, yes, you can do this with the regular ESX .iso file, but you’ll need to purchase licensing for those installs eventually. You can register ESXi for free use!