ok by following theog steps the things get worse. Now when I boot it gives me a screen which says. A recent hardware or software change have been installed a file that is signed incorrectly or damaged, or that might be malicios software from an unknown source.
If you have a Windows Installation disk bla bla bla
Otherwise, to start Windows so you can invastigate further, press the ENTER key to display the boot menu, press F8 Advanced Boot Options, and select Last Known Good Configuration
Info: Windows Cannot Verify the digital signature of this file