Windows busts a valve at random stuff all the time. I plugged my USB headset in after launching a game the other night and my PC hard locked for whatever reason.
I had a nosebleed in the shower once... Thought it'd be funny to rub it all over my face then shout to my girlfriend for help. She immediately crumpled into a blubbering mess and would have been no use if I was actually seriously hurt. :|
You can launch it from Run with powershell, you can launch it from the Start Menu by searching for powershell, you can launch it by pressing windows key + x and selecting Powershell from the context menu.
@Vikas That account is definitely not a standard account. You should expand that folder in Windirstat and see what it contains, if it is nothing you need, delete it.