There's no more audio when I play files on my computer? The video works fine.

So this is my mother’s computer. It’s a desktop and it runs Vista. She’s kind of technologically challenged so I keep having to fix things for her. Recently, the audio won’t work in VLC and Windows Media Player. The video works fine in VLC. I feel that the culprit is WMP (it’s version 11) but of course I could be way off, but no matter what I do I can’t get rid of it or reinstall. I installed K lite codec pack to be sure, and I restored the computer to an earlier point (I’ve also rebooted plenty of times), but no go. The type of file doesn’t matter, songs/movies/etc all the same.

Here’s how I know it’s not a speaker issue though, YouTube and other browser audio/video work fine. This computer has had virus issues in the past (and I’m sure it’s not completely clean yet). I’ve considered doing a factory restore but it does have a lot of files so I’m trying to keep that as a last option.

Any suggestions at all? Thanks for reading :)