(PC) Can't find answer myself, Need help with video

[Zippoflames]

Hey guys,

I need a bit of help with something on my pc that keeps happening and I don't know how to fix it or how to word it correctly on Google to find an answer...

When I watch any videos on YouTube/media centre etc. I get borders appear at each end of the film and they come and go as they please.
Sometimes it happens top and bottom but normally just the sides get it

I'm not sure if it makes sense what I'm trying to ask but its bloody annoying lol

[lockblock]

When you say they come and go, does that mean the same video has it for a bit then goes away or one video has it and the next does not?
Assuming the first there is nothing you can do about it short of resizing the picture in a custom player like xbmc or maybe vlc.
Another thing to note is assuming that the video wasn't encoded for whatever aspect ratio your screen uses you should just watch it as is vs stretching the picture out or clipping part of the top+bottom or sides.