I've found a program called nav.exe; some google searches have told me its a virus, others say its safe. I used to have Norton Antivirus but my subscription expired, I have reason to believe this may be a virus, as it seems that fake updates have been installing, I am unable to upgrade to windows 10 (I run on 8.1), and my PC has slowed down significantly. My disk, according to task manager, has always been at 100%. nav.exe, according to my resource monitor, apparently is writing at almost 2 million bytes per second and reading at 137 bytes per second. What should I do?