To those that downloaded the FREE vmware esxi hypervisor and are playing around with it it's not intuitive at all where to enter the license information.
You will get the license key with the product download
If you don't enter the license key it will expire after 60 days.
What you have to do is logon on to your Vsphere client and sign in to the host ESXI server (real host or VM depending where you installed it).
Go to SOFTWARE in the configuration tab and under licensed features you'll see AT THE RIGHT HAND SIDE of the screen small BLUE text mark EDIT.
Click this and then you can enter your license number --then you are all set.
I've enclosed a screen shot. Now to get some REAL Virtual machines working. !!!!
When I've got time amd stuff all working I'll try and create a decent tutorial for setting everything up, configuring the data stores, installing a Windows XP and a Windows 7 Virtual Machines with passthruh and how to import an existing vmware workstation / player vm into ESXI.
I'm still learning as I go along however so it might trake a little time. I've posted snippest so I can refer to them later without forgetting a few weeks later.