WHY is this happening?

[Windows Central Question]

I've got a nokia lumia 520 with widows 8.1 OS, and i recently have removed and placed back its screen (unscrew the back, put out the motherboard, put out the screen... place everything back) just from curiosity and now, when i am trying to open it, it appears the nokia logo, and then a blue screen with an unhappy face. Why is this happening? Because of me (removing the screen?). Or what? I'm not sure if i have to soft or hard reset it. Please some HELP!

 

[Harrie-S]

Yes, this happened probably during the repair. You have now a system error.
First try a harde reset.
http://www.windowsphone.com/en-us/how-to/wp8/settings-and-personalization/reset-my-phone

If that does not work use the Lumia software recovery tool.

https://forums.windowscentral.com/e...singleTopic%26topic%3DFA142987&token=3KmxCY4T