Reformat old computer hard drive

Maybe I should bite the bullet and take it to a repair shop, the computer is old but works fine just the dam messages that it does not recognize the monitor, or the mouse or the keyboard or the hard drive! until the wife wanted to see the USB stick that a friend lent her to see some animal videos and that did it, the main monitor is a 27" inch TV.

Thanks you all for the advice, I will see what the technician says, I hope I do not need to buy a new one.

navegator