Windows 10: Windows profile suddenly gone and stranger's in place

I was previously signed onto my account and was about to log into a game with my friends for a session, but it suddenly froze. I waited for almost 20 minutes before I pushed the power button and forced it to restart.However, when it went to the sign-on screen, my profile wasn't there and instead someone else.That profile is the seller who sold me this computer almost 3 years ago.I tried restarting multiple times, advanced restart, shutting it down for an hour.I even tried the system restore option, but the Seller's profile is still there and is the only profile there.I tried the password he pr

:)

 

Why did the startup window get cleared?

I didn't missed any step, the list was gone and gone , even after using lot of programs the programs were not listed in that list.

 

CCC Profiles that disappear

id suggest a spyware check

 

Lost default photo viewer after profile rebuild

Thanks Brink. I've tried those steps before i started searching Google. After the profile rebuild i don't have the Photo app listed to choose to make it default in either the system settings for default apps or the Open With option.

I can't even find it doing a search. Seems to have been removed somehow with the profile rebuild, which doesn't make sense.

Might be helpful to list what i've done I've done the open with check, the choose default program in the system menu, tried that in device manager default programs also. I've checked the programs and features Turn windows features on/off and it's not listed there (never thought it was but that was a suggestion), searched the MS Store, it's not listed there either.

I don't like playing in the registry unless i have defined steps and haven't found anything for this yet, just the Win7 version like in my OP.