My screen's gone darker

[MaggieW]

I've got a new Dell laptop and someone else, who's not contactable just now, has used it and made the screen a lot darker. How do I adjust it to lighten it please?

Also, they've obviously tinkered with a setting which means it powers down, not just goes to screensaver, and I'm not sure the quickest way to get it going again, or indeed adjust it so it doesn't do this.

Help gratefully received!

Don't have a clue but my brother does that all the time to my Mum's pc. He adjusts and downloads and poor Mum has to try and get it back to normal. Bloody rude. He is not getting on my pc.