I have a Windows 2008 SP2 Std VM in ESXi that has changed itself from thin provisioning to thick. At first I thought it was something I did. I have a base machine that is thin. I use converter standalone to do V2V and make sure the new machine is thin.
Then, I do updates, reboot here and there and somewhere along the way it changes itself to thick. I've repeated it a few times today thinking I must be mistaken. At this piont I'll live with it, but would like to know why so I can learn. Perhaps I can prevent it next time.