Replying to Computer Question (Video Editing Specific)

Okay, so my computer is 4 years old now and I know I need to upgrade cause none of my videos will render any more. At least halfway through they fart out and tell me that I need to close some programs to make more memory available. Little does my computer know, I've gone through and closed everything that isn't required in the rendering process. Literally. Searched for spyware dozens of times and this is as good as it gets. With that said, to those of you who are editing higher res shots from HD cams and camcorders like a 7D or HVX, how much ram do you have on your computer? And what kind of processor? Im trying to figure out how far I need to upgrade