Hi
I'm afraid that I'm out of ideas, what's weird is that this happens on both versions of Windows.
Normally you would expect to see this as an error in the Windows configuration, but this seems more like it has something to do with the boot setup.
One last thing you could try is to, download and install easyBCD.
It will let you easily manage boot setup for multiple operating systems or repair the boot files, even create a new boot setup.
I'm not exactly sure what you need to do once you get into it, but I've used it to change boot order, etc.
But it is supposed to be able to repair boot problems.
I always have it installed on my computer, it's small, easy to use and it's free...