Screen got all the sudden Huge!

My Computer is actually quite old and key combinations dont work so when i do crtl + - Nothing happens also i talked to a friend of the matter and they told me to check zoom i did so and it was at 100% im not sure if this computer's old age is affecting the problem.

Ill give a summary of what happened exactly I Logged into the computer And a black screen with a blue box showed up saying "No Signal" I was confused but in a few seconds it loaded the home page of my computer but everything was huge i was very confused but tried to load up my games anyway so i was about to get into Minecraft when I did it said it crashed loading it up and in details it basically said the screen size was a problem i tried a few different thing informing me the screen size is a problem. This computer is 8 years old so some things may not help or work with it. Thank you in advance for any information you can bring about this.