I recently learned about an issue with the VMware Compatibility Guide that is creating some confusion. The problem (demonstrated in the screen shot below) is when when using the compatibility guide to search for Guest OS support on ESXi there is no option for selecting versions prior to 5.0.
What happened is prior to vSphere 5.0 the Guest OS support for both ESX and ESXi was listed under a single product name of “ESX”. However, with 5.0 a new product name was added called "ESXi". An unintended side affect of doing this is now when selecting ESXi you only see ESXi 5.0 and not the earlier versions.
To help clear up any confusion, the Guest OS support for a given release is the same for both ESX and ESXi. For example, to list the supported Guest OS for ESXi 4.1, you query for ESX 4.1. Starting with 5.0, which is ESXi only, you will need to use the product name “ESXi”.
I hope this will help clear up any confusion. Hopefully, we'll see an update to the website to help address this as well.
