Packard bell easynote error message

Firstly

I am not very technical with computers. I have here a Packard Bell easynote BU45 lap top.

I have just changed the screen and I switched the computer on and the initial Packard Welcome came up so iassume the screen is working fine? but I have an error message Reboot and Select proper device or Insert Boot Media in selected Boot device and press a key_ with a flashing cursor when I press it it just duplicates down the page.

Any Ideas as I say I am not very good on the tech side just need a lay mans version if poss please of what is happening and can I rectify it? as my local computer shop want £50.00 just to look.

Whatever change you made, must have affected something, adversely.
You could boot into safe mode to undo your change to the screen (whatever that was) or do a Windows System Restore to date prior to making your change. - If you are not technical, or have not used safe mode before, find someone to guide you through it.