When I play online games, such as WoW, CoD, etc. I lag BADLY when my sister plays music and/or checks her facebook on her computer. I think it's just my horrible internet provider service, but if there is another way to fix this lag, please tell me. Thanks
yes, your sister is putting a hurt on your online gaming if she's doing what you say. i suggest you work things out with her so you both don't share the internet at the same time. general surfing by both at same time should be okay though.
It's not the ISP, it's the fact that streaming media and downloads like to grab as much bandwidth as they can. You need to get a "gaming" router that has options to limit how much bandwidth is used for services or certain computers.