Clock lost time then my computer froze and wont power up

[hpxt978]

Hi I'm new here and was hoping I could find advice, I have an old HP Pavillion XT-978 yesterday I realized my clock was off then this morning I found it was way off and my trend micro virus had run it's nightly scan mabey more fore all I know because of the clock going haywire, but it was frozen on the virus scan page, I tried to shut it down by holding the power button in but to no avail I cut power to it replace the clock battery iside a cr 2035 and cleaned all the fans wile in there, and still will not turn on. I have a green light on the back where the power supply is, but nothing else no fans no beeps just silence Does any one have any idea;s besides time to pull the plug for good!