Did you try a different mouse? Perhaps it is having issues.
It doesn't really sound like anything else to me. Hard drives usually dont give much warning before they fail - they just do. In my years of computer nerding, I've probably had about 4 drives fail on me. None of them gave warning - they just went dead. Same with the 2 fried motherboards I've had.

As far as viruses/malware, take this advice from a total computer nerd: Get a free antivirus called Avast. I have used it for years and it has caught everything without ever once recognizing something as a virus that was not. Look up reviews of it if you'd like - it's considered one of the best, if not the best, out there - free or otherwise.