Can't start my computer

Greetings. I am sure this identical problem showed up sometime, but I can't find it and I am desperate. My computer is quite old, but had a new hard drive installed a few months ago. I have windows XP installed and I must have gotten some kind of virus, because it doesn't start. It shows me the screen asking if I want to start windows in safe mode and with every option I choose it loads for a minute and then just restarts again, giving me the same screen. I tried to format my computer, but I can't change the CD to the primary device, because it just beeps every time I try to hit the any of the 'change values' buttons.

If anyone knows how to save my computer and if it's not too late, I desperately ask you to help me. I could really appreciate your help at the moment.