I'm almost certain I have a virus. I've run Mccafee, CCleaner, and all of the programs you asked, and nothing can be found.
Basically, after I start using the internet, my computer will eventually slow down, then disconnect from the internet, then go to where nothing else can be done and the computer needs to be restarted. This all happens within 1-2 minutes.
Can you help me? Please let me know if you need anything else, thank you.