Create ESXi 5.1 bootable USB key
If you want quick and easy way to build bootable USB key with vSphere 5.1 ESXi version under Windows 7 or any other Windows flavor Linux Live USB creator is the tool which you are looking for. Easy to use and fast. All credits goes to Wojtek 🙂 http://wojcieh.net/
If you are Linux user follow official VMware documentation.