Tech support

Two or three days ago I started having trouble with my computer. Every time I try to play a media file, whether it's Windows Media or Quicktime, it comes out all jittery, like a skipping CD or DVD. I ran a full virus scan on my computer, but it didn't help. At this point in time, nothing else has been affected, and it's not just one program, since as I said both Windows Media and Quicktime files have been effective. So what could it be? I first noticed the problems when I came home from work in a day when there had been a power outage, so perhaps the blackout had an adverse effect on a piece of hardware in my computer. But I'm not computer-savvy, so I wouldn't have the slightest clue how to check. Has anyone out there had problems like this, and if so, how did you solve them?