I can't possibly explain what happened in your setup. I can only think of two responses:

1- I wouldn't trust Windows with anything other than a brand new installation on a blank drive (if dual-booting, doing two clean installs). It's too messy for me to trust Windows with anything more complicated.

2- Windows 7 is without a doubt my favorite version of Windows ever made. I know others disagree, and I really liked 2000, but 7 is the one for me.

Basically, I'm saying your subject line isn't wrong, it just might be a little too unspecific

As far as I'm concerned, Windows 8 is a complete and utter failure. If Microsoft doesn't do a better job with 9/whatever, I'm moving away from Windows entirely or running Windows 7 until it stops getting security updates...