Boot the PC and keep tapping the delete key until it enters set up, look for and load performance / enhanced BIOS defaults, press F10 then press enter, type Y to confirm then press enter, as it boots, keep tapping F8 until you get options, select safe mode to see if Windows will load
If it does, reboot, keep tapping F8 until you get options, select safe mode with networking to see if it loads
If it does, check the firewall is running, look for updated drivers for the video adapter, or you can re-instal from the software CD
Some keyboards will show boot order if you tap F8 so you would need to tap F5 in this case