Because I had XP and Linux running with Windows 7 and Windows 8.1 (and a bit of Android and whatever crap all the other toys use) and it all worked fine. Then when I rebuilt the XP box and put Windows 7 on it, it still worked fine, so I didn't bother with homegroups because I didn't think it was a good idea to poke at a network that worked. I only had a problem when I put Windows 10 onto the Windows boxes and the account thing kicked in.
I just rebooted my laptop, first time since installing WinX. My usual password didn't log me in. Realised it had decided to use my Hotmail as the user account. I use KeePass for Hotmail passwords so had to find my silly long password on my phone.
And I noticed some strange things happening like the icons in the taskbar being hidden my the Cort Ana and task buttons but that was due to still having Start8 installed.