No screen signal after replacing harddri

I have a 1.8 GHz P4, with a 64 MB Geforce TI 200 graphics card, 768 MB SD RAM, and a brand new 160 GB Seagate harddrive after replacing the old harddrive that broke. When I start my system, no matter what CD’s or floppys (XP install CD, XP boot floppys, 98 boot floppy) I put in the drives, it does not boot. It seems like everything is running and powered, the cords are fine, but the screen display nothing, it does not even recieve a blank signal. Please help, I have no clue on how to get on.