g'day Donna.

You don't happen to remember seeing an error number do you?

Hard to know without having read the message.

Has anyone made any changes to the inside of the computer - like add anything or done some major update lately?

Having that error number would be really helpful.

edited to add: You say you can't use the computer.

Do you mean that it starts up but you can't connect to the internet or do you mean it won't start up?
What happens exactly when you boot the computer?