Acer aspire desktop running oddly

Hi!

My son (who is currently in the navy) has an Acer desktop (AM1641, windows vista) that he left here at home. When he left we cleaned it out well (it was quite dusty) and I ran some anti-virus scans on it and did updates before we put it away.We ran it off and on for a few days after we did these things and it seemed fine.

I needed to hook it back up so I could grab some files for him, and it is now behaving strangely, when certain programs such as control panel, internet browsers and even malwarebytes and S&D are started they flicker and the screen changes resolution. Once these are turned off the computer returns to 'normal'. Media programs such as Media player classic look and play just fine.

Any thoughts? He has a laptop with him where he's at, but I'd hate for him to have this computer stop working as it has a lot of his files on it.

I can't go back to a restore point on windows as apparently he'd never set one up (my bad, I expected him to do more of that for himself).

Thanks in advance for your thoughts, Liz

 

Thank you for your response.

It is just flickering when programs are open.As soon as they close, the screen looks fine.

I will check the cables to the monitor again. The monitor is also several years older than the computer, so if that doesn't help I might even plug in another to see if that has something to do with it.

Also thanks for suggesting safe mode, I didn't think to try it last nite.

 

Thank you for the suggestion to check the monitor wires. Turned out to be the wire on the monitor end that was loose, which I wouldn't have thought of right away. It's working great now!