hello
how did you create the usb boot stick?
in the passed i always used hp usb creator utility
http://h20564.www2.hp.com/hpsc/swd/public/detail?swItemId=MTX_2aa85604194243afbdb1c29a34
dont know if it still works for windows 2012 servers
i dont understand. are you trying to install esxi 6 on windows 2012? or installing windows 2012 on esxi 6?
i always use the iso to install windows. just connect to local iso image from the console
if your trying to install esxi 6 first check HCL list
and most of the time i use custom HP image
https://my.vmware.com/web/vmware/details?downloadGroup=OEM-ESXI60GA-HP&productId=491