This could be several things but really sounds like a virus. If you don't
have any files that you HAVE to save, you can re-install the operating
system. If you can't even log in you are not going to be able to use a virus
removal tool. First I would try re-installing the BIOS to see if that will
correct the issue. You can find info about the BIOS on the manufacturer's
website.
Or, if you have a friend that it tech savvy, they can take your hard drive
and put it in their machine as a secondary hard drive to detect the virus.
At the very least, they could back up your files and you can re-install
Windows.
