I just received it yesterday, an Acer Aspire 5516 laptop, and when i try starting it up it goes to the black screen and tells me i need to check my cable and that it cannot find the operating system. What do i do to fix this?

Is this laptop brand new? If so, if I were you I would take it back, or send it back. When you first get a laptop, it probably needs to have the AC adapter plugged into it for a while before you start up the computer, for at least a couple of hours, because the main battery probably needs to be charged, and if it does, it probably won't run even when the AC adapter is plugged in, or it won't run for long. If the main batterry is not charged enough, the computer may not boot into Windows, or it may boot into Windows but the computer may shut down in a short time, but if the main batterry wasn't charged up enough and you have the AC adapter plugged into it that would NOT cause EITHER of the messages you are getting. "check my cable" If you don't have the AC adapter plugged in, in theory you could get that message, but otherwise you should NOT, whether you have an external monitor (that is powered on) plugged into the laptop or not. "cannot find the operating system" That means it's not finding an operating system on the hard drive. When you first get a computer the boot order in the bios Setup is set up correctly such that the hard drive is listed in the boot order list in the right place. The only reason you MIGHT get that message, other than the hard drive is defective, if the boot order is correct, is if you plug in a non-bootable USB flash drive, or you have a non bootable disk in your optical (CD or DVD) drive while booting and you pressed a key to boot from it and of course it won't boot - some bioses won't try the next thing in the boot order list if the first thing is not bootable. . You or someone could go into the bios Setup while booting to check to see if the boot order is correct, or you or they could load defaults in the Setup which would probably cure problems caused by improper Setup settings, but it's NOT normal for bios settings to be improper when you first get a computer, and otherwise that "check my cable" message is NOT normal for a laptop, if the AC adapter is plugged into it.