this is where I fell out before.
It is asking me which Windows installation would you like to log onto. it is a one letter field answer.
If you don't have a backup, then you will need to spend some time determining which is the boot Windows and which is an extra one (you only have one active boot Windows). It sounds like you reinstalled Windows without having it overwrite your prior install, so now you have two. If this is the case, at least you have a working hard drive.