I don't really understand what you mean. Can you boot into any operating system? Can you boot up a Windows install DVD?
Which exact ROM did you flash in? I hope you got the right one.
The one everyone uses that is on macrumer if you google gtx680mac rom. I can load efi bootloader to select mac or windows and the apple or blue window and spinny thing starts up then 5-10 s later it freezes there. If it's the wrong rom I saved the old rom so not a huge deal, but I just want to know what is happening at the moment.