computer turns off by itself

[jonathanjd]

My computer keeps turning off by itself when I leave it unattended for about an hr or so. I suspect it's a malware/virus issue, because I was stupid enough to let my antivirus expire for a wk before getting it renewed. I've checked the computer's "power save" options and it's not supposed to shut down like that. It's also plugged in so it has plenty of power. Any help is greatly appreciated!