How to adjust laptop screen resolution?

My laptop (Lenovo Z50) can only support videos up to 720p. If I tried to play a 1080p video on my media player or YouTube it will constantly lag or sometimes the video freezes or turns grey and I have to pause and play to make it normal again which is frustrating if I'm watching a long movie.

Can anything be done? Or is my laptop preset to only support up to 720p?

Lags… You pause… You wait… Then you can watch… I feel that this is what is called " buffering "… The video is not coming in fast enough in order for you to view it without having to pause so you can load up more video… This is generally caused by a slow server where the video is… Or-r-r-r a slow internet connection… Or if you are using Wi-Fi, you do not have enough bandwidth.

It's not your laptop, it's your internet connection speed. I have a monster of a computer, and i can't watch anything over 720p either.