Do you get the option to enter BIOS? If not then you need to buy a new computer ($300 walmart), and a external USB/Sata(??) connector to remove the 'old' computer hard drive and make it accessibe externally (not Windows nor Programs, just your data like Documents, Photos, etc.).
If you can get into BIOS, check under drives, do you see the Hard Drive listed? If not then the HDD failed, so need to get a new drive install it and hopefully you have all your DVDs (Windows, Drivers, etc.) to reinstall everything from scratch.
If you see the HDD, then when you exit BIOS and it reboots, you see BIOS again start tapping F8 (NOT HOLD - JUST TAP TAP TAP) and can you bring up the options in Windows to get to Safe Mode? If yes then what happens in Safe Mode? If no, then you need to get the DVDs to reinstall everything from the ground up.