|Try to boot into Windows Safe Mode to see if your mouse will then work. Watch the first screens at start up to see what keystroke/s to use.|
After you get this issue sorted out, consider yourself lucky that you dodged a bullet. Many things can happen to a computer that will result in data loss. You should always maintain a LEAST two copies of any personal data. Even more if the data is irreplaceable. Burn to optical disk and then make copies. Keep a least one copy off site. OR if you are lazy, consider cloud storage solutions.