I don't know exactly what's wrong with the signal I'm getting on my TV?

I just wanted to know what makes my TV snowy? It's not very snowy but enough that you can visibly see it. Is it because I have it hooked to an old VCR or that I have to much plugs in one outlet or is it because I need a new TV(or all of the above)? I don't think it's because the wires in the back of the TV need tightning because it's pretty much tighten all the way. And when I turn on my PS3 it has scrolling lines going up and down with background buzzing noises and when I play games it makes it seem pixelated in some areas. I have a prong adapter but it doesn't really do anything. It seems that when I read some posts of people who get HDTVs had the same problem with their old TVs but is perfectly fine since they got those TVs. Would that actually cure some of my problems? If not, why bother making HDTVs when they have the same problems as well?