So this problem has me a little confused:

I have an "old" Dell PC with an ATI 128MB gfx and on-board audio. Normally this PC is good for all sorts of every day stuff except gaming. Since i bought a new and better PC about a year ago the Dell has been serving as a media-center in the living room.
I use it for playing music and i watch XviDs and DVD's through the S-video out on the Gfx card. And for these things it works flawlessly. I have had no issues with the quality of the images or with the audio.

Recently i started trying to watch streamed content from websites like surfthechannel and so on, but i quickly found that no matter what TV-show or movie i tried to watch the audio would rapidly fall out of sync with the images, to the point where stuff becomes unwatchable.

I thought that it might be the old and "chronically ill" windows installation that was to blame, so i reinstalled windows with only the necessary drivers(latest versions), VLC and Power DVD(no anti-virus or firewall since this PC can just be wiped if anything/one should find it's way in)
The PC is still great for music and visual content, but streamed media still falls out of sync just like before that reinstall.

So what should i try?
It makes no sense to me that i should have this problem with streamed content.

Thx for replies and good suggestions