How do you know a virus has entered your computer?

Answer 1

Sometimes when a virus infects your computer, there are no visible signs at all. In these cases, the only way to tell would be to have a working anti-virus program, or to recognize the virus yourself when you are examining the list of running processes in task manager. Other times though, viruses to give signs that they have infected your computer. One of the most common sign is your computer slowing down or becoming unresponsive for no apparent reason. Viruses may also display pop-ups on your desktop or insert ads into webpages.

Answer 2

It's temperature gets higher.

Put a wet flannel accross the monitor and give it some hot soup through the DVD drive.